Subordinate charm for automatic backup

[Vincenzo Di Somma]

Hi all,
as a prove of concept, we worked on a juju subordinate charm to easily 
perform backups.
The idea is that the subordinate charm has no configuration, the 
principal charm instructs the subordinate on how to perform the backup.
Backup can have very complex use cases, to avoid to get swamped in long 
discussions, we cut it short and decided to use duplicity and to support 
Ubuntu One and S3 as backend.
While the charm still needs some clean up, it works pretty well.
You can find it here:
https://code.launchpad.net/~vds/charms/trusty/jujubackup/trunk
Thanks,
	    vds