Adding cleanrc target to remove all rc_* depending files

This adds a new target that removes all rc_* depending files. When doing an `source rc_*`, this is all that is needed to reset your application. The following make all is much faster.

This is aimed to be more consistent with our deploys as we reduce the amount of regeneration of files to the absolute minimum.

A simple `make cleanrc all` in the post-restore-code hook is now enough to assure this during deploy, as it generates the rc_* depending files and runs the unit tests, but it does not recreated all build-artefacts. Note that we can't do this as of now because of missing phantomjs on our production servers, that's why deploy hook adaption is not done as part of this PR.