Install PPA-Purge With Multi-Arch Support In Ubuntu

The ppa-purge package available in the official Ubuntu repositories is not multi-arch aware, so purging PPAs like xorg-edgers or gnome3 doesn't work correctly on 64bit systems.

A few hours ago, thanks to Tim Lunn's work, a branch that adds multiarch support has been merged into the main ppa-purge branch, fixing this bug. The fix should be available in Ubuntu 13.04 Raring Ringtail soon, but I don't know if it will be backported for older Ubuntu versions so to make this fix available for Ubuntu 12.10 and 12.04 users, I've uploaded the latest ppa-purge from BZR to the main WebUpd8 PPA.