Refactor: create actions and drivers

[dergachev]

This will allow pulling out a gem "vagrant-multiprovider-snapshot" into a generic API gem, with vagrant-vbox-snapshot and vagrant-vmware-snapshot as specific implementations.

See:

• https://github.com/scalefactory/vagrant-multiprovider-snap/tree/master/lib/vagrant-multiprovider-snap/command
• https://gist.github.com/teamon/5178811

[dergachev]

Not a priority.