remove unused tunneldigger package and feed
use dedicated functions to checkout svn/git repos

increases readability of get_source()
Generalize handling of feeds and packages

* Simplifies adding new feeds and packages
* Better separation of implementation and configuration
* get rid of having to modifiy another file when adding
  feeds(build_patches/feed.conf)
Merge pull request #22 from meskal/reworkFeeds

Rework feeds