Adds initial files for layman sync plugin
Adds --storage cli option

argsparser.py: Adds --storage cli option.
layman_.py: Adds subprocess use of --storage flag.
In order to respect the location of the repository defined by repos.conf
the subprocess now specifies the storage location.
layman_.py: Overrides default storage value for API

The default storage value will be overwritten upon initialization
of the LaymanAPI in order to respect the location reported by
repos.conf. Checks have also been added to ensure the location being
reported by the LaymanAPI is the actual location of the repository
reported by the repos.conf file. If it is not, then the LaymanAPI
will be re-initialized with the new storage location.
reposconf.py: Adds sync-type checking
reposconf.py: Adds branch and layman-type info to config
layman_.py: Adds create_overlay() function
layman_.py: Cleans up msg declarations
layman_.py: Adds proper function docstring
layman_.py: Adds exitcode evaluation for API variant sync plugin
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.
layman_.py: Adds remote list fetching
layman_.py: Updates overlay description requirements
Merge pull request #13 from twitch153/sync-plugin

Adds support for a portage sync module along with the ability for the user to specify the overlay storage location via a cli option.