Fixed regression in resource list editor where it'd get fucked if the user has non-standard UI scaling enabled

- 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)

Visual Mode: fixed an issue where the crosshair was distorted after the viewport was resized. Fixes #321. Fixes #777

Fixed an issue where textures OBJ models with w components in their texture coordinates were not displayed correctly. Fixes #775

Linedefs Mode: fixed a problem where the "Select Single-sided only" and "Select Double-sided only" actions would still display the selection numbers of deselected linedefs

- Sector Color Picker: fixed a problem where the dialog could not be closed using the "enter" or "ESC" buttons
- Light/Sector Color Picker: fixed a problem where closing the dialog would result in a flicker
- Light Color Picker: fixed a problem where canceling the dialog would not revert the color settings

Fixed a problem where grid transform didn't work when the new origin had an x value of 0. Fixes #769

Added explicit warning if gzdoom.pk3 is not loaded for GZDoom game configurations.

Fixed tokenizer not picking up the very last token in the stream.

Fixed a problem where the flags selection form could be too small to accommodate the "OK" button when the game configuration contained too few flags

OBJ Models: fixed a crash that occurred when the usemtl directive had the texture to use in quotes. Fixes #758

Texture set definitions can now be imported/exported to/from game configurations using configuration files

Fixed an issue that allowed to open Hexen format maps with a Doom format game configuration when using the "Open Map in Current WAD..:" feature.

Sound Environment Mode: fixed an issue that caused building sound environments to fail when the arguments of the Sound Environment thing had unexpected values.

Sound Environment Mode: fixed a crash that happened when exiting Draw Lines Mode with the "edit" action and returning to Sound Environment Mode. Fixes #755

Things: fixed an issue where inserting a new thing would not immediately apply ZScript user variables

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