Add Environment Helpers installer framework
    
    Environment helpers are meta-plugins that allow to set ipsilon in
    well defined environments.
    For example when ipsilon is install in a FreeIPA or AD domains and
    authentication methods, cetificate, keytabs etc, can be pre-configured
    and deployed at the same time the server is installed with minimal
    effort and wellknown methods.
    
    These are run before any of the other plugins as they can chage the
    configuration option for any of the plugins, enable or disable plugins,
    or pre-configure some elements.
    
    Signed-off-by: Simo Sorce <simo@redhat.com>