Code review comment for lp:~gary-lasker/software-center/recommended-installed-feedback

Ok, I've added more unit test cases, done a lot of refactoring and cleanup around this area of the code (lots of FIXMEs cleared) and at this point the branch should be ready for review again. You can review the changes in detail by looking at the checkin comments starting at rev 3094.

Many thanks for your review, as always!!