re-work rps_checkNeededPackages allowing required packages to be passed to it.
change the previously unused checkForInstalledAPTPackage to be less verbose and make use of it
added gcc-4.7 as a required package
use rps_checkNeededPackages for installing dependencies. Less verbose, and means we don't have to launch apt-get when not needed
Merge pull request #382 from joolswills/depends

Depends