various changes to help debug render pipeline
- fixing some cases where TREE_SCALE was not using constant in prep for making TREE_SCALE larger
- added createLine() to VoxelTree
- added axis lines made of voxels to scene
- added corner points made of voxels to scene
Merge branch 'master' of https://github.com/worklist/hifi into render_voxels_optimization
Merge pull request #186 from ZappoMan/render_voxels_optimization

Some more tweaks to test pipeline