Fixed two crashes that happened when trying to reset the grid transform, or toggling the grid visibility while no map was opened

Visplane Explorer Mode: fixed an issue that caused a crash when the map doesn't have nodes the Visplane Explorer Mode understands. Fixes #736

DeHackEd: fixed and issue where the "#" in "ID #" fields was erroneously interpreted as a comment. Fixes #735

DECORATE/ZScript: fixed an crash introduced in 070aa9f3 that happened when a base actor didn't have a thing type info

DECORATE/ZScript: fixed an issue where setting the thing category using the editor key didn't work for replaced actors. Fixes #729

Visual Mode: fixed an issue where using the "apply camera rotation to things" action did not update the thing cages properly

Eternity Engine game configuration: clarified description of the "impact" UDMF linedef flag
Eternity Engine game configuration: added missing "monstershoot" UDMF linedef flag

Fixed an issue that prevented models from being loaded correctly when some model indices in MODELDEF were unused. Fixes #727

The installer will not try to create an icon on the common desktop anymore, but on the user's personal desktop

Draw Settings docker: fixed an issue where toggling the texture check boxes stopped texture overrides from being applied

 - using "-map" with lower case parameter doesn't crash anymore
 - using "-cfg"/"-config" with a non-existing configuration file doesn't crash anymore

Map element associations: fixed a problem where things that have a argument of type tag set to 0 were referencing all things with tag 0. Fixes #718

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

UDBScript: fixed a problem in the voodoo doll example script when the "looping" option was set to true

ZScript: fixed an issue where #include files were not parsed when the parent file had a //$GZDB_Skip comment. Fixes #716

Added command palette that allows the user to search for (and execute) commands at any time. Unbound by default. Resolves #555

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

Edit Selection Mode: improved handling of texture transformation (still doesn't work 100% correctly)

- The updater can now update itself

Map Analysis Mode: fixed an issue where lines were erroneously reported as overlapping in certain situations. Fixes #713

Nodes Viewer Mode: the mode will not engage anymore if ZNODES are found, do to ZDBSP reordering the vertices when rebuilding the nodes. Addresses #659

Visual Mode: Fixed a problem where using visual sloping a slope handle around itself resulted in invalid slopes