Refine single-instance cheking.

 - Improve the display message
 - Change the location of lockfile from .config to .cache
 - Check for the script name to decide if it is really another instance
   of UTT running. Changed to fix rare bugs (eg: LP: #1170571)
battle-proof the single instance dbus stuff
Merge pull request #123 from jokerdino/master

Update changelog and pot files
Update po files
Fix long line warning in debian/changelog
Update changelog to include FFe bug report