Configure cobblerd and cobblerd.service

Since cobblerd no longer is guaranteed to be installed into /usr/bin .
Remove install_data=/usr/share/cobbler/ from setup.cfg.

Makes it impossible to install into a different prefix (eg. /usr/local).
Make docpath relative.

Makes it possible to install into a custom prefix.
SQUASH ME: Find out with what :)
Rather involved patch. Implement a sbin_scripts distutils option

I am trying to figure out if its possible to upstream that (distutils or setuptools)