Removed unnecessary markPageStale invocation in put* from
PagedByteBuffer.
Cleanup: Superfluous model in BackdropSystem.
Adjusted startupLogo to fill window in EarlyLoadingScreen.
Bugfix: Co-modification risk in ProjectileBehavior's possibleTargets.
Bugfix: Co-modification risk in CollisionManager's collideables.
Misc cleanup: ThreadManager.