[NEEDS WINDOWS BUILD CHANGE] research tools

[dexsda]

This PR adds a few features I used during research for the e4m3 3:42. The functionalities are off when demorecording.

• Edict tracking, for following what a certain monster does to figure out better ways to manipulate them
• Extended bbox drawing, mostly for convenience of finding secrets but also to easily get edict numbers
• A grenade trail mode (called 'billiards' mode since it looks like oldschool billiards games drawing of the ball path) that allows figuring out alignments and crossfires

I don't have a Windows machine to test building on, so this requires adding the billiards/ dir and headers to the build.