Quick patch for Apex S11 support

Should remove an error on loading Apex Legends maps released after S11's November 19th patch

Brush Entity Palette

All brush entities now generate coloured geometry
Still a few bugs with geometry quality in places

Trigger Brush Geometry

This was spurred on by the TF2 Speedrunning bounty on sp_boomtown / Abyss 2
trigger_* brush entities geometry is now generated automatically on load

Initial Release

Copied from bsp_tool's raw .blend map importer
Now properly integrated into the UI
(No progress counter yet)