Rough first pass at asset change detection on disk
Pull loose asset file watcher out to its own compilation module
- Pull edit-time force fully loading of packages in AssetManager out to editor level as ForciblyFullyLoadedPackageManager
 - Renamed AssetManager to AssetTracker
Some cleanup with the asset tracker and loose asset file watcher
Have editor do asset loader ticking in separate thread and proxy events through a threadsafe event buffer that syncs on a wx timer. Allows for backgrounded asset load/caching.
Removed the tracker since it's now redundant with engine-level tracking
Cleaned up init code for project panel, fixed project failing to load on my machine (and I would expect on most people's machines? platform specific maybe?)