Add disabled repository example to factory
Add chroot_scripts as attribute to Autoyast export

The apply_repositories method needs to also add commands to
the chroot_scripts. Since it wouldn't make much sense to write
a separate method for these we convert chroot_scripts to an
attribute and rename the dependent methods according to this change.
Optimize Autoyast repository export

Make sure that disabled repositories are also disabled in the
installed system and set all other repository options which are
not supported in Autoyast via zypper.

Fixes #460
Merge pull request #465 from SUSE/fix_460_2

Fix 460 2