Keep rover from driving on undrivable squares

The current implementation assumes that the rover's parent frame of reference is the world frame of reference.  We should switch the call from translateBy to worldTransformBy, but currently there is a bug in that.
Moved blockly behavior to rover
Merge pull request #22 from virtual-world-framework/branch/collision-detection

Branch/collision detection
Added basic terrain height following using scene.raycast
Added radio asset (may need to change texture format)
Added Radio and Icons
Replaced dds textures with png
Fixed spacing
Removed unnecessary client check
Removed pointer distance check
Change case of radio.png inside collada file.
Merge pull request #21 from virtual-world-framework/branch/radio-module

Branch/radio module
Refactored per code review notes
Follow terrain if the duration is 0
Factor out terrain height calculation
Merge pull request #23 from virtual-world-framework/branch/terrain-height-following

Added basic terrain height following using scene.raycast
Resolved conflicts
Updates from the branch/blockly