[util] add angle_frame
[ent] Make biped look at focus
[ent] Bit of reorg an uncomment-out a fixture check I forgot to uncomment-out
[ent] Some tweaks
[phys] Add Filters
[phys geo] Make Filters work
[ent] Use phys::Filter::active instead of b2Fixture::isSensor to turn off fixtures
[ent] Fix ground_velocity direction issue
[ent] Fix collision issues by having separate feet fixture
[ent] Fix biped not looking at focus when standing still
[ent] Fixed biped's feet falling asleep :)

No really, the bug was that the ground-walking system can't auto-wake bodies, so once the b2Body fell asleep, you couldn't move until you jumped or crouched to wake it up.