Merge pull request #1205 from ZappoMan/bugfixes

implement ReadWriteLock for VoxelTree to fix crashes in VoxelServer
Merge pull request #1207 from ZappoMan/bugfixes

added debugging to JurisdictionMap for server crashes
only call deleteLater for linkedData if we have a QCoreApplication instance
only attempt to deleteLater on linkedData if it exists
Merge branch 'master' of github.com:worklist/hifi into assignment
Merge pull request #1214 from birarda/assignment

fix for deleteLater on Node linkedData
fix thread contention issues and VS crash on domain server shutdown and restart