Remove temporary files

[stafio]

As frail mentioned in another post, I think it would be a good idea to have a simple utility to get rid of unnecessary files that can use up a lot of disk space over time.

A utility to:
1) apt-get clean
2) Clear ~./thumbnails

...as well as any others. I'm not too familiar with all of the places that temporary files can accumulate. I'm sure many others aren't either, hence this suggestion.