Base implementation of the popup menu and speedrunner mode in Jak 3.
Autosplitter is untested because I'm on Linux.
Also a couple of other misc changes:
- Model replacements can now have custom bone weights. Needs the "Use
Custom Bone Weights" property (provided by the OpenGOAL Blender plugin)
enabled in Blender.
- Better error message for lump syntax errors in custom level JSON
files.