Add distribution-karaf subproject to archetype-md-sal-app-simple

The idea is to have a very simple project that allows the developer to have a running karaf container that runs their feature (and pulls in any needed dependencies).

I think the best way to do this is to use a variation of the dance used in integration of pulling in the zip file from controller (but for the opendaylight-karaf distro) and having resources with appropriate config files to automatically load the developers feature. Such resource files would get copied into the unpacked opendaylight-karaf.