`Projector` loops over all visible objects using `o` as the loop variable, but another loop inside that one also uses `o`.  Since `var`s are function-scoped, not block-scoped, this can prematurely advance the outer loop and skip rendering some objects entirely.

Removed IndexBufferAttribute. Promoted index attribute to BufferGeometry. Maybe .addIndices() instead?
/ping @benaadams

Store reading and writing to `.offsets`.

Avoid mutations to `.drawcalls` from outside the `BufferGeometry`.