Some cosmetic changes in Bit flags form.

Fixed: Incorrect articles were sometimes used in Draw Geometry/Curve/Rectangle/Ellipse info messages. 

Classic modes, UDMF: floor/ceiling texture offsets can now be locked in place while sector is dragged.
Fixed another bug in Tools.autoAlignTexturesOnSidesUDMF()
Replaced Math.PI-related equations with stuff from Angle2D class.

Rectangular Selection: removed direction-based additive/subtractive selection. You can now hold Ctrl to enable subtractive selection, hold Ctrl-Shift to intersect with existing selection.
Point Thing at Cursor action: action now works when used from menu, changed default shortcut to Shift-L. You can now hold Ctrl to point Things away from cursor. 

Tag Explorer, UDMF: when item's comment editing was canceled, item's comment was removed instead of leaving it unaltered. 

Fixed a crash after drawing a sector when a newly drawn line completely matches already existing one.
Fixed a typo in documentation.
Fixed a typo in actions description.

Paint Selection, Sectors mode: when selection is started over a sector, it's selected state is now toggled properly.
Several small fixes in "Raise/Lower sector to nearest" action.

Preferences form: list of actions already using current shortcut was not updated properly when actions list was filtered.

Visual mode, "Lower/Raise Floor/Ceiling to adjacent sector" actions: you can now hold Ctrl to lower/raise sectors to lowest/highest sector inside selection.
Visual mode: added "Align Textures X and Y" action (default key is Ctrl-A).
Preferences Form: Actions can now be filtered.

Visual Mode, UDMF: "Auto-align Textures Y" action now applies vertical scale of first (highlighted) surface to the rest of aligned surfaces.
Linedef Edit Form, UDMF: lower sidedef texture offsets were never displayed.
Some more changes in auto texture alignment of newly drawn lines.
BuilderEffects plugin should compile now.

Visual Mode: added "Lower Floor/Ceiling to adjacent sector" and "Raise Floor/Ceiling to adjacent sector" actions.
UDMF texture offsets are now used when splitting a linedef in UDMF map format.
Some changes in auto texture alignment of newly drawn lines.

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.

Brightness Mode now uses the same selection methods as other classic modes (e.g. Paint Selection and Subtractive Selection)

Fixed: "Automatic clear selection in classic modes" option was broken.

Texture browser can now show flats/textures only.

Fixed incorrect behavior when 2 linedefs are merged into one after deleting a vertex, when a newly created linedef overlaps existing geometry.
Visual Vertex handles were not updated when sector's floor or ceiling height was changed.

Fixed a possible bug in Visual vertex handles rendering code.

Updated ZDoom ACC to r3889.

UDMF: vertical offsets of a vertex can now be edited in Vertex Edit form and are shown in Vertex Info panel.
Bridge mode: when source sidedefs don't have upper/lower textures, their middle textures are used instead.

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

Rendering of (G)ZDoom rendering effects (slopes, 3D-floors etc.) can now be toggled in GZDoom Visual mode (default key is "Tab", action is Visual modes -> Toggle GZDoom rendering effects)