RearView Tools

- moved to separate class
- new icon/button for restore view
-
click mirror behaviour

- shrink function - restore mirror window view and set forward
fullscreen view
reset view

- reset icon
- resetView signal
added population data back for SIMPLE_CHILD_ARRAY implementation
moved blended _children union into BLENDED_UNION_CHILDREN
clean up voxel server stats page
added SIMPLE_EXTERNAL_CHILDREN mode, which saves on most of our child VoxelNode children storage without being too complicated
Oops; I broke the voxel attachments.
Merge pull request #1131 from stojce/19443

Code Review for Job #19443
Merge branch 'master' of https://github.com/worklist/hifi into ick
Merge pull request #1136 from ey6es/ick

Fix for voxel attachments.
Fix for arm on old skeleton.
Merge pull request #1137 from ey6es/ick

Fix for arm on old skeleton.
add mutex for _nodesRequestingJurisdictions to fix crash
Merge pull request #1139 from ZappoMan/voxelnode_memory_savings

VoxelNode memory savings
Merge pull request #1138 from ZappoMan/bugfixes

add mutex for _nodesRequestingJurisdictions to fix crash