OBJ Exporter: replaced default folder selection dialog with something more convenient (and more consistent with the rest of the program)

Fix exception caused by horizontal mouse wheel (resolves #409 reported by ioan-chera, reported by KanaiZo)

OBJ Exporter: checking the "Solid" checkbox now adds to following flags to the actor: INVULNERABLE, NODAMAGE, SHOOTABLE, NOTAUTOAIMED, NEVERTARGET, DONTTHRUST

Add support for Line_SetAutomap{Flags,Style}

OBJ Exporter: improved exporting models for use in GZDoom. It can now export models that can be directly used in GZDoom, and also creates the necessary MODELDEF and ZScript/DECORATE code

Image exporter: added options to use sector brightness for the export, create brightmaps (based on sector brightness), and split the image into 64x64 tiles

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

3D Floor Mode: fixed a crash when duplicating 3D floor geometry and there was not enough space in the control sector area

Fixed a bug introduced by addressing #427 that stopped the script editor to show up in vanilla Hexen. Fixes #429.

Fixed a problem where translucent 3D floors were drawn solid. The cause was a rounding error because of the transition from float to double.

The script editor is now only shown if the current game configuration supports scripts. Resolves #427.

Fixed a crash in the DIALOG/SCRIPTS editor when selecting any other than the first two options in the "look in" combo box in the replace tab. Fixes #425.

Draw Ellipse Mode: fixed a rounding error that could result in wrong shapes under certain conditions

Edit Selection Mode, Flat Align Mode: fixed a bug where snapping occurred to wrong positions on lines when the grid was transformed

Draw Rectangle Mode: fixed a problem where the guidelines were not displayed correctly under certain conditions

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

Vertices Mode: the preview vertex is now correctly shown on intersections between the closest line and the transformed grid

Added some error handling to duplicating 3D floors

Changed how performing undo interacts with volatile modes (it will now actually perform the undo instead of just canceling the volatile mode)

- Added preliminary code to remove new 3D floor control sectors when pasting was canceled after duplicating 3D floors