This makes it easier in the spec files, e.g. in conditionals

Also, colorful diffs

It was incorrectly set also set for the "System" repository there, which
caused software there to be built incorrectly (with the micro arch
flags) and in the wrong location

Repos were missing reference to the home: 'System' repo

I suspect the dependency solver copes better that way. Not sure though..

The previous fix only worked in the 'gcc_6' repo itself and not in
dependent repositories such as cuda_10_0_gcc_6.

Apparently something has changed upstream and openSUSE has not yet
tracked this in their prjconf, added here meanwhile

Previously, the logic decided that it didn't need to look at the
sub-projects, as the main package is disabled. However, if it was
previously enabled the --disable didn't touch the branched packages in
the sub-projects and those stayed enabled.

- Had old logic for distribution
- Removed '--all' flag to disentangle functionality
  Use mpcdf_setup_subproject if you want to re-create all enabled
  repositories for all packages