Sectors Mode: fixed a problem where dragging a single highlighted sector did not move the things in the sector when synchronized things editing was enabled

Added autosaving of the current map. Autosaving happens in intervals when the map is changed. It will not overwrite the current map, but rather create new files, just like backups. Autosaving interval and number of files can be configured in the "Recovery" tab of the preferences. Autosaving can also be disabled there (not recommended). Autosaves will not have their nodes built for performance reason.

Fixed a problem where not selected geometry and things could not be dragged when the "don't move selection if any part of it is outside of map boundary" option was enabled

(Text labels are removed because of performance issues)

Added action to change the index of linedefs, things, sectors, and vertices. Can be accessed through a shortcut (not bound by default) or the menu of the respective mode (#903)

Behavior can be configured in the "Toasts" tab in the preferences.

Tag Range plugin: fixed a problem where the new tags were not displayed in Sectors Mode when selection numbering was disabled. Fixes #795

Sectors Mode: fixed a regression where sector labels were not updated after editing sectors. Fixes #793

Fixed a regression where editing map elements did not preserve the selection order, but used the index order instead. Fixes #791

- editing a highlighted, not selected map element will deselect other selected map elements, then start editing the highlighted map element
- dragging a highlighted, not selected map element will deselect other selected map elements, then start dragging the highlighted map element
- dragging a single map element will keep its selection state. I.e. dragging a selected map element will not deselect it after dragging anymore
  - dragging a highlighted, not selected thing will not select it after dragging
- dragging a highlighted, not selected sector, while other sectors are selected, will only drag the highlighted sector, and not the selected sector (and deselect the selected sectors)

Sectors Mode: fixed a crash that could happen when the mouse was moved out of the map control while an UDBScript was modifying the map

Snap selection to grid: fixed a problem that could cause a crash if geometry got removed by snapping it to the grid

Added map scripting capabilities to UDB (#656). Documentation at https://biwa.github.io/udbscript-docs/

Don't use thread unsafe collections in threaded code (hopefully fixes crash in Sectors Mode when selecting sectors)

Increased performance on multi-core CPUs when selecting sectors in Sectors Mode when Synchronize Thing Editing is enabled

Sectors Mode: fixed a crash when merging sectors while a shared linedef between them was shown as an association

Sectors Mode: fixed a problem where things were not selected correctly when synchronized thing edit was enabled

Linedefs Mode, Sectors Mode, Vertices Mode, Sound Environment Mode, Sound Propagation Mode: slightly improved performance when moving the mouse

Editing modes: fixed some crashes related to undoing/redoing while objects with associations were highlighted

Sectors mode: fixed a bug where applying floor and ceiling brightness gradients didn't work correctly

Sectors Mode: fixed a bug that could cause a crash when drag-selecting over areas that contained sectors after deleting those sectors

Improved associations and event lines. Refactorings to make the whole thing more sensible (hopefully). Options to display labels on event lines (can be configured in Preferences -> Editing).

Sectors Mode: the sectors things are in are only determined if necessary, which should increase performance when switching into Sectors Mode in very big maps

Things Mode: performing the smart grid transform action will now set the grid origin to the selected or highlighted thing
Sectors Mode: performing the smart grid transform action will now reset the grid transform

Removed lots of unnecessary casts to float of the Math methods. Also removed some other minor implicit casts

Added option to lock texture offsets of 3D floors when dragging the tagged sectors

- Added option to enable additive paint selecting without holding shift independently from regular additive selecting

* Mouse selection threshold

* Cleanup

* Fix selection bug

Added, Errors and Warnings window: most of warnings/errors related to (G)ZDoom text lump parsing can now be double-clicked to show warning/error source in the Script Editor.
Fixed: some map format conversion errors were never displayed, because errors list was cleared after performing map conversion.
Fixed: 3d floor indicators in 2D modes were not updated after leaving Visual mode.
Fixed: some UDMF-only interface buttons were never removed after converting map format from UDMF.