editVoxels.js updates: clipboard support, multitouch orbit, and better support for "larger" voxels

* change calculateVoxelFromIntersection() to act like the C++ code in cases of target voxel size larger than the intersecting voxel size.
* added cut/copy/paste support
* changed VoxelsScriptingInterface to modify local tree as well as send messages to server - closes #2058
* added "selection" tool to the tool palette
* made tools on tool palette be sticky/clickable
* capture +/- keys while running editVoxels.js
* improved zfighting for selection
* added place holder for pan support
* added support for multi-touch orbit and pan support
* added Voxels.getFaceVector() to help with scripting
* added Voxels.getVoxelAt() - closes #2018