Clone specific repositories as well

This will add a functionality to clone specific repositories
from ownCloud organization.

It also generates an error if the core environment is not set up.

To use: `python3 -m ocdev setup <repositoryname>`

The conditions for base and core are added because otherwise
the setup command could be used only once
Yes, but you cant assume that people run it in the owncloud directory. They should be able to clone them anywhere :)

Base just clones them into apps because the owncloud directory is known