Removing legacy references to Electric now that we're using tags &
branches properly.
Adding Husky SDF file (no wheels yet)
Proper physics settings
Now with wheels and proper folder structure
Switch quaternion reference from Bullet over to tf
Adding meshes from husky_description. Revising launchfiles to add
environment variable tweak for plugin/model path mod. Modifying
husky_base launchfile to launch SDF properly (note: Gazebo issue #5611
still applies at this point, but seems to work despite the error)
Doc tweak