First pass at adding proxy support for providers needed for kitchen drivers
Changes to add metal provider registry
Removed ActionHandler from VagrantBox where (needed for VagrantCluster, tho)
Moved some internal provider retrieval logic to metal from kitchen driver
Helper isn't needed for machine_file
Refactor of action_handler for correct class scoping/etc.
Renamed provider variables to action_handler for clarity; additional comments;
Added inflate to base class
Changes based on jkeiser's review comments; mostly minor cleanup
Fix error with generating vagrant cluster path
Merge remote-tracking branch 'origin/dt/driver-surgery'

Conflicts:
	lib/chef_metal/provisioner/fog_provisioner.rb