Fixed several issues with "Synchronized Things Selection" setting:
- Things were not deselected after dragging a single sector.
- Things were not deselected after editing properties of a single sector.
- Things sector references were not updated after using "Join Sectors" and "Merge Sectors" actions.
- Things (de)selection is now applied to all things, instead of only the ones visible using current Things Filter.
Sectors mode: removed "Move Things in Selected Sectors" toolbar button.
Sectors mode: added "Synchronized Things Editing" menu item, action and toolbar button. When enabled, things dragging will be synchronized to sector dragging. Regular, Paint and Rectangular selection will also select things (holding Alt while selecting inverts this behavior). Deleting sectors will also delete selected things.
Linedefs mode: added "Synchronized Things Editing" menu item, action and toolbar button. When enabled, selected things will be dragged when dragging linedefs. Rectangular selection will also select things (holding Alt while selecting inverts this behavior).
Changed: selection info now always displays info about all types of map elements.
Fixed: .dbs containing only current map settings was created when trying to save unchanged map.
Fixed, Visual mode, "Copy Texture" action: when "Use long texture names" option is disabled, texture name as stored in Sidedef should be used, not the 8-char texture name.
Updated documentation.
High-DPI: fixed many issues with incorrect controls size (Tag selector width, Comment Editor size, icons size, tabs size etc.).
Cosmetic: changed map geometry dragging undo messages to more descriptive ones.
Fixed, Textures Browser, cosmetic: "Show textures in subdirectories" checkbox should be repositioned when "Long texture names" one is invisible.
Updated ZDoom_DECORATE.cfg (added A_SetFloatSpeed + a couple of fixes).
Changed, Things mode: things are now rendered with a bit of transparency, so things beneath other things are now visible.
Fixed, Things mode: in some cases it was impossible to highlight a thing beneath other thing when their positions were the same.
Changed, 2D modes: changed thing bounding box and arrow image.
Fixed, cosmetic, 2D modes: in some cases thing arrows were rendered bigger than thing bounding boxes.
Fixed, Texture Browser Form: well, I broke "Tab" key functionality again (in previous commit)...
Maintenance: changed curly braces style to match DB2 one (hopefully not breaking anything in the process...).
Maintenance: changed private method names casing to match DB2 one.
Sectors mode: changed Alt-key handling. Now it only enables "snap to grid increment" mode.
Things mode: "snap to grid increment" mode now works in this mode.
Updated documentation.
Error checks: added "Check unused textures" option.
Replaced MissingTexture3D and UnknownTexture3D.
Sectors mode: restored "Lower/Raise Floor/Ceiling by 8 mp" actions.
Visual mode: in some cases sidedefs were rendered as selected when they were not.
Existing linedefs were not split while drawing new lines in some cases.
Texture and height overrides were not applied correctly in some cases.
Preferences form: "Ctrl+Alt+ScrollUp" and "Ctrl+Alt+ScrollDown" dropdown items were setting the shortcut to "Ctrl+Shift+ScrollUp" and "Ctrl+Shift+ScrollDown".
