Structured Objects

Introducing structured objects to the "island" world. Structured objects are matrices of colored primitive shapes. If the "StructuredObjects" world adapter is being used, these shapes and colors are visible to the agent.

In this early implementation, the agent cannot move with this world adapter, and will always simply load the closest world object into his scene object.

A single first structured object, "Tree", has been implemented. Scene drawing in the client was out of scope for this feature branch, only minimal fixes to the JS client have been made.