Create `stormpath import` Command

[rdegges]

This command should let you do stuff like:

$ stormpath import postgres://user:password@host/db
$ stormpath import
Please select the type of database you'd like to import: [postgres|mysql|mongodb|...]:
$ stormpath import postgres://user:password@host/db --username uname --given-name first_name --in-application myapp

This will let developers easily import existing Accounts into Stormpath.