Visual mode: fixed a crash when trying to move texture offsets of invisible sidedef.

UDMF fields, handled by UI, had broken field types after r1758.
Removed some redundant type casts.

Visual mode: texture offsets are now clamped to texture size when dragging textures with mouse.
Visual mode, UDMF: when gravity is enabled, sector gravity now affects camera movement.

Textures were not loaded properly from PK3/PK7 archives.
Visual mode: restored ability to remove textures using Delete action.
Visual mode: fixed several bugs in Cut/Copy/Paste things actions.
Visual mode: vavoom style 3d floors were not displayed properly.
Visual mode, 3d floors: added support for "RestrictLighting" (2) flag.
Visual mode, 3d floors: inner sides of 3d floors with "swimmable"/"render inside" flags used incorrect brightness value.

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, 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.

Visual Mode: You can now Shift-Select (usually Select = LMB) to select all adjacent surfaces with same texture, Ctrl-Select to select all adjacent surfaces with same height.
Added Selection Groups options to Edit menu.
Selection Groups can now be cleared using either Edit -> Clear Group or Ctrl-Shift-[group number] shortcut.
Toolbar button groups can now be toggled using context menu. Hold "Shift" to toggle several button groups at once.

Merged Visual mode and GZDoom Visual mode into GZDB Visual mode. GZDoomEditing.dll is no longer required.

Added UDMF Controls plugin.
Added "Snap selected vertices to grid" mode (Found in Edit menu).

Doom-style walls shading is now applied in Visual Mode

@ more fixes for auto-aligning hi-res textures: now takes the WorldPanning flag into account

- Fixed a problem in the linedef info panel where the linedef numbers was displayed instead of the sidedef number
- Fixed a problem where dragging geometry and things onto the window title bar locked up DB2
- Fixed a problem with wrong texture offsets of hi-res textures