Documentation and some cleanups

I wrote some documentation for building with the piratebox_feed variant.
I also added some additional build targets for those steps that did not have any.

Carefull: __auto_build_stable__ now does a __clean__ as first step, deleting all dirs created through the build process. It also cleans the local_feed folder. I am not exactly sure if this is a good idea.

I removed comments from the Makefile and moved them to the README.
Also refactored the Makefile a little bit, regarding whitespaces and comments. Moved comments in front of a make target. When you now run make without parameters a list of all make targets is shown, also a hint to read the README.

Also I am starting the repository server in the background and log to a seperate file, so we can automatically move on with the next steps without blocking the Makefile. Although I need to test this.

I created a directory to hold various config files, for now only the kernel config has its place there.

My next step will be to adapt the documentation for the __local_feed__ method.
After this I will make all the needed targets and documentation so we can have a build bot and build daily snapshot versions. At least I think this is what we want ;-)

Let me know what you think about the modifications.