Added snapshot support using either VSS (win xp/vista/7) or LVM (linux).
Using the snapshot feature requires administrative/root privileges, and is toggled by the "snapshot-policy" option (by commandline or in advanced settings).
Also improved the validation of options to not show incorrect warnings.
This fixes issue #233.
git-svn-id: https://duplicati.googlecode.com/svn/trunk@461 59da171f-624f-0410-aa54-27559c288bec
kenneth.skovhede@gmail.com