Updated Unreal model loading to the fixed behavior in GZDoom - axes were remapped incorrectly (I blame Marisa_Kirisame)

Actually fixed vertex axes in Unreal models.  Fixed the order of rotations in MODELDEF Offsets (this was not releavent to Unreal issues)

Added simple Unreal model support;  Fixed numerous issues with normal handling;  Fixed outright invalid handling of AngleOffset/PitchOffset/RollOffset in MODELDEF

Fixed: GZDB was built against wrong SlimDX version (including 64-bit which was built against 32-bit SlimDX) - (reported by StrikerMan780, leodoom85, Rockstar Racoon)

Fixed (?): The new .NET 4.6.x JIT method inlining was fucking with GetCallingAssembly-based plugin detection

Fixed: on a second thought, let's just make FileImageReader fall back to guessed image if possible...

Fixed: made more correct checking for legal file formats; now it should actually validate the format upon loading

Fixed: flats are now unconditionally detected as Doom Flat if they are exactly 4096 bytes long and inside F_ markers or flats directory.  (reported by Chickenlegz)

Enabled parsing of NaN in UDMF so that the existing buggy maps load;  made it throw exceptions when a NaN vertex is added to the map

Did some maxcode refactoring about dynamic lights;  added initial spotlight support (at least they are recognized as lights now)

Added support for non-1.2 pixel ratios if view stretching is enabled (reported by Nash);  Fixed: map names in quotes were not recognized properly.

* Mouse selection threshold

* Cleanup

* Fix selection bug