Independent window for adding PPAs

Considering the goal of Linux Mint of being easy to use for anybody, I believe it is necessary to have independent access to the PPA tab in Software Sources, just like now it is possible to have independent access to Software Sources instead of having to open Synaptic for that.

The motivation is the following. If you want to have the latest version of your favorite software and you don't want to wait a year until it is included in the repositories, you may want to add the developer's PPA. PPA? What is that? Where do I add it? Well, I don't care. I just want to get it done. So I go to the Mint menu, type PPA, open *Add PPA*, paste `ppa:developer/software`, the cache is automatically updated and then I am prompted if I want to go to the Software Manager or better yet, this happens automatically.