Fixes reloading config file for remote_db

utils.py: reload_config() function has been added

layman_.py: When calling an api function such as .get_available()
you would previously not get any custom overlay definitions listed
in the output, in order to fix this the layman sync plugin makes use
of the new reload_config() function to reload the config and get the
custom overlay names.
config.py: Adds output attribute for OptionConfig
layman_.py: Adds repo installation

If a repository is specified in the repos.conf config file and it
doesn't exist in the list of installable overlays an overlay.xml
definition will be created for that overlay and it will be
installed.