Add GSH as a loader job type

https://spaces.at.internet2.edu/display/Grouper/Grouper+-+Loader+GSH

A GSH job type will allow more kinds of sources in loader jobs. The script could be written to query a REST endpoint, a flat file, or a proprietary client-server interface, and then produce either a list of subjects (GSH_SIMPLE) or groups + subjects (GSH_GROUPS_LIST). The wiki proposes the subject and group resolution be done in the script rather than outputting then as strings. This is so that the script has total control, in case it needs to do more complex logic – e.g. custom display names or descriptions for groups, or dynamic source determination for subjects.

Like gsh templates and reports, there will be specific variables passed into the script. GrouperSession and LoaderJobBean objects will be used like in the SQL and LDAP loader types, while a new GshLoaderJobResults object will hold the rows of the script results. for a GSH_SIMPLE job the rows will be Subjects, while for a GSH_GROUPS_LIST they will be Group + Subject tuples. It will not need a separate group query like the SQL loader does, because the script will be doing its own group creation as needed.