add appliance_console Prompt#ask_for_string

- can use just_ask, but this is more similar to others
- support net/ssh in prompt specs
- present? not available outside of rails

https://bugzilla.redhat.com/show_bug.cgi?id=1138723
appliance_console#local_database?, #database?

- needed for key generation logic

https://bugzilla.redhat.com/show_bug.cgi?id=1138723
appliance console key_configuration fetch

- use ssh to fetch
- many more parameters into key_configuration
- separate key_configuration setup from exec
- auto generate key if local database (and no key)

https://bugzilla.redhat.com/show_bug.cgi?id=1138723
suppress mount warnings in specs
Merge pull request #528 from kbrock/appliance_console_copy_keys

Appliance console copy keys