Populate Inspector-ready components

[ngokevin]

Will start populating with components that would do well from the Inspector (i.e., have an immediate visual effect that don't need to be composed with other components).

• [x] ocean
• [x] particle-system
• [x] physics

There are other great components that function better from code/HTML...we can perhaps add those after.

[donmccurdy]

I've pulled physics into its own repo, aframe-physics-system (better ideas on naming?), with the exception of kinematic-body. I'm going to put kinematic-body into aframe-extras.misc instead, to discourage it more actively for VR apps.

[ngokevin]

That sounds good, want to do the honors of updating the registry?