remove some unecessary null pointer checks
added rectangular range limits
fix bug in editVoxels.js that wasn't deleting menus
fix potential crash in setIsOptionChecked() added support for positioning separators
Don't simulate avatars' models when they're being rendered as billboards.
Closes #2165.
Merge pull request #2167 from birarda/null-checks

remove some unnecessary null pointer checks
Merge branch 'master' of https://github.com/highfidelity/hifi
Merge pull request #2168 from PhilipRosedale/master

added rectangular range limits
Merge branch 'master' of https://github.com/highfidelity/hifi
Merge branch 'master' of https://github.com/worklist/hifi into bugfixes
Merge pull request #2169 from ZappoMan/bugfixes

Menu scripting bug fixes
fix a flipped null check
Merge pull request #2173 from birarda/null-checks

fix a flipped NULL pointer check
various particle crash and deadlock fixes
Merge branch 'master' of https://github.com/worklist/hifi into bugfixes
keep known nodes alive when we receive a packet from them
Merge branch 'master' of https://github.com/highfidelity/hifi
Fix for annoying "QThreadStorage" warning.
more octree locking cleanup
removed some debug