Add basic host management with drivers
Make driver an option of "hosts create"
Remove redundant ToJSON method
Add support for setting options on a driver
Remove unused error from NewStore
Add support for choosing host with -H
Display error if url not passed to socket driver
Rename Driver.Name to DriverName for clarity
Add basic virtualbox driver

Creates a host that doesn't do anything.
Make socket driver options private
Store socket URL as property of driver
Fix valid host name regex
Print full command name in subcommand help text
Add support for removing virtualbox hosts
Pass through host directory
Add starting and stopping virtualbox hosts
Add start and stop commands
Display driver and state in host list
Add error to GetURL
Rename disk to disk.vmdk