Sector info panel: floor/ceiling brightness should be always shown when "lightabsolute" flag is set.

Rewrote VerticesMode.DeleteItem function. It was still not working properly after previous commit (proper vertex deletion can become surprisingly complicated in some cases)...

Visual mode: you can hold Shift while dragging a texture to lock movement to horizontal axis, and Ctrl to lock it to vertical axis.
Color Picker: fixed a crash when entered float values were not in 0.0 - 1.0 range.

Visual mode, UDMF: OffsetX and OffsetY were not properly taken into account in "Fit Texture Width/Height" actions.
UDMF: different Sector Edit Form is now used in UDMF map format.
Some fixes in Linedef edit form.
Added missing icons.

Visual mode, UDMF: added "Scale Texture Up (X)", "Scale Texture Down (X)", "Scale Texture Up (Y)", "Scale Texture Down (Y)" actions. Default keys are Num6, Num4, Num8, Num5.
Visual mode, UDMF: renamed "Rotate Thing Clockwise" and "Rotate Thing Counterclockwise" actions to "Rotate Clockwise" and "Rotate Counterclockwise". These actions can now be used to change rotation of floor/ceiling textures.
Visual mode, UDMF: "Reset Texture Offsets" action now also resets sidedef's scale and floor/ceiling's scale and rotation.
Visual mode, UDMF: control line's OffsetX and OffsetY were not taken into account when calculating texture offsets of 3d floors' sides.
Visual mode, UDMF: fixed a ton of bugs in Auto align functions.
Visual mode, UDMF: when using "Move Texture Left/Right/Up/Down by 1" actions texture offsets were not updated properly when texture's scale was < 1.0.
Visual mode, UDMF: OffsetX and OffsetY were not taken into account in "Fit Texture Width/Height" actions.
Dockers Panel: added Pin/Unpin button, which acts the same as "Preferences -> Interface -> Side panels -> Auto hide" checkbox.
Texture size labels can now be disabled by unchecking "Preferences -> Interface -> Show texture and flat sizes in browsers" checkbox.
Texture size labels now are not shown for unknown textures.
Most of texture size labels had incorrect bg color.
ZDoom_linedefs.cfg: action specials 223 and 224 had incorrect Arg0.

Visual mode: fixed a crash after disabling GZDoom rendering effects (Tab key) when visual sector was not created for sector with 3d floor's control linedef.

+ some fixes to previous commit.

Fixed several bugs in Engine selector dialog ("Game configurations -> Testing").

Linedef edit form: action arguments were set to zero when settings were applied to several lines with different argument values (instead of being kept unchanged).

Linedef edit form: all linedef UDMF properties are now editable via user interface + some fixes in sidedef UDMF controls. 

Fixed a typo in one of Visplane Explorer messages.
Small fixes here and there.

Increased screenshot jpeg quality to 90.

"Clear Group" 2-10 actions had incorrect default shortcuts.

Added some boilerplate to SaveScreenshot function.

Default flag ("playercross") was not set when a map was converted to UDMF map format (because there are no default flags in UDMF).
Linedef activation now translates a bit more accurately when converting a map to/from UDMF.

Screenshots of GZDB window and edit area can now be saved (Tools -> Save Screenshot and Tools -> Save Screenshot (edit area)).
NumericTextbox now uses NumberDecimalSeparator instead of CurrencyDecimalSeparator.

Map Analysis mode: only a single undo is now created when multiple similar errors are fixed using "Apply to all errors of this type" checkbox, which greatly reduces errors fixing time.

Vertex edit form: it was impossible to enter fractional position and zOffset values even if map format supported it. 

"thingflagstranslation" block was missing from UDMF game configuration, so thing flags were dropped when map format was changed to UDMF.

Removed some unused "using" directives.

Linedefs mode: added "Align Floor Texture to Front Side", "Align Floor Texture to Back Side", "Align Ceiling Texture to Front Side" and "Align Ceiling Texture to Back Side" actions (available in Linedefs -> Align Textures menu).

Visual mode, UDMF: "Auto-align textures" actions now work for floors and ceilings. Textures are aligned to a linedef of highlighted floor/ceiling, which is closest to 3d-cursor position.

Added "SetCVarString", "SetUserCVarString", "GetCVarString" and "GetUserCVarString" functions to ACS configuration.

Linedef colors were not updated properly when a map format was changed and were causing an exception in some cases.
Vertices mode: linedef in split linedefs range was redreawn incorrectly in some cases.
Updated "Sector 3D Floor" (160) action: set default Type to Solid (1), added "Use Arg5 as Line ID" flag to Types, changed arg5 name to "Line ID / Hi-Tag".
Added "GetUserCVar", "SetCVar" and "SetUserCVar" functions to ACS configuration.
Set width and height of several actors to 0 in game configutrations (non-zero sizes were added as a workaround when GZDB was not displaying actors with 0 width and height in Visual mode).
Added several sprites to game configurations.

Classic Modes: added 3D floor indication (color can be changed in Preferences -> Appearance -> 3D Floors).
Sector_Set3dFloor action (160): added hi-tag/line ID check.

Visual Mode, UDMF, Visual Vertices: heights of vertices without z-offset was incorrect in some cases.
Visual Mode, UDMF, Visual Vertices: vertices without z-offset are now rendered using Vertex color (Preferences -> Appearance -> Vertices).

Visual Mode, UDMF: added "Fit Texture", "Fit Texture's Width" and "Fit Texture's Height" Actions.cfg
Visual Mode, UDMF, Visual Vertices: you can now press "Delete" key to clear z-offsets of selected vertices.
Visual Mode, UDMF, Visual Vertices: the logic, which decides whether z-offset should be kept or removed, was not working properly.
Visual Mode, UDMF: Auto-align Textures (Y) action was not working properly when targeted texture was lower wall without "Lower Unpegged" flag.