adding support for better multithreading in VoxelTree
Merge branch 'master' of https://github.com/worklist/hifi into threaded_voxel_server

Conflicts:
	libraries/voxels/src/VoxelTree.cpp
	libraries/voxels/src/VoxelTree.h
threads for persist and packet processing
removed old dead code
dead code cleanup
flush delete queue after encode is complete
fix comment
fix comment
fix comment
Merge branch 'master' of https://github.com/worklist/hifi into threaded_voxel_server
Merge pull request #880 from ZappoMan/threaded_voxel_server

Threaded voxel server- Fix "freezing" on hq