Coding standard cleanup and VoxelNode optimization
- make octalCode and children members private
- add public getters for accessing these private members
- change constructor to require an OctalCode for all non-roots
- default constructor constructs a rootNode
- make primary access for deleting, adding, and accessing children through public methods that do bookkeeping
- calculate AABox on voxel creation so that we don't need to do all the math when we deal with voxels
- added methods on VoxelNode for common items like getCorner(), getCenter(), getLevel(), etc
short circuit shouldRender logic in treeToArrays()
Merge pull request #197 from ZappoMan/render_voxels_optimization

Voxel Persistence in server, voxel-edit tool for creating voxel files, new VoxelTree features
Merge branch 'master' of https://github.com/worklist/hifi into render_voxels_optimization