rosie.ws_client: store password in gnomekeyring

Prompt username and password with `zenity` or `raw_input` and `getpass`.
Introduce `rosie hello` for users to set up connection.

Close #1255.
Would anyone not have [this package](http://rpm.pbone.net/index.php3/stat/4/idpl/20039475/dir/fedora_18/com/filesystem-3.1-2.fc18.i686.rpm.html)?