New string for translation for Ubuntu One Control Panel

[Natalia Bidart]

Hi all,

Thanks to this bug report 
(https://bugs.launchpad.net/ubuntuone-control-panel/+bug/746370), we 
realised we had a .ui file that wasn't being listed in the ubuntuone 
control panel's POTFILES. I've fixed that, and I letDavid Planella know 
on IRC, and he mentioned I should notify both ubuntu-translators and 
ubuntu-doc.

This adding introduces a new string that will require translation: "Sync 
locally?"

Sorry for noticing this so late in the cycle.
Cheers, Natalia.