Change dev build/Unity editor support to actually work, AFAICT.

[NathanKell]

• The test was not reporting accurately. Now we call the proper Unity property to check.
• Mainthread queued items were never being executed in the editor.
• We were running things out of order, and hanging the game from that (in CreateVoxel).
• Thus I have removed the delegate stuff in CreateVoxel and replaced it with a check to whether we're in debug mode; if not, behave as we used to (avoid the CPU spike); if so, do a different way of checking for a destroyed geometry module
• In addition, avoid an unassigned reference exception when checking the rb of a compound part.