overlay.py: Improves dictionary checking logic
Adds initial files for layman sync plugin
sync/__init__.py: Adds description for "new" action
layman.py: Moves API initialization to separate function

Also adds new() function for subprocess variant of layman plugin
module.
layman.py: Adds fully functional api sync
layman.py: Adds api variant of new() function

Also cleans up output messages as well as some variable
interpolation.
Renames sync dir and plugin name to "layman_"

This change has been made to prevent loading the wrong layman
modules and causing conflicts when using the portage sync plugin.
layman_.py: Adds re-initialization prevention code

This commit prevents unnecessary re-initialization of the LaymanAPI
in the layman sync plugin module.
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.
reposconf.py: Adds sync-type checking
layman_.py: Adds checks to ensure repo location

Previously it was made so that the initialization of the LaymanAPI
wouldn't occur if it already existed. This could however lead to
reporting the incorrect storage location for repositories reported
by repos.conf. Checks have been added to ensure that the LaymanAPI
will be re-initialized if the storage location reported by repos.conf
differs from what was already previously reported.
Adds layman-overlay-maker tool

This tool has been made to assist users in creating their own
layman overlay definitions.