Expose useful defaults on AtomsAttributes

[andrewkaufman]

It is currently functional but not very useful. It also needs unit tests.

[andrewkaufman]

For example, the attributes that usually come out of the Generator should be listed here as options (so someone can lookdev using those attributes without requiring a crowd sim).

user:atoms:agentId
user:atoms:agentIdStr
user:atoms:agentType
user:atoms:birth
user:atoms:direction
user:atoms:frameRate
user:atoms:gravity
user:atoms:groupId
user:atoms:groupName
user:atoms:id
user:atoms:layoutPosition
user:atoms:lod
user:atoms:orientation
user:atoms:position
user:atoms:scale
user:atoms:selected
user:atoms:state
user:atoms:turnAngle
user:atoms:up
user:atoms:variation
user:atoms:velocity