Add a "create_or_update_user" function to hu_pin plugin, and have all places that create a user use it.  The "pin3_create_user" filter function now passes along API data to the aforementioned function.  pin3 authenticate function has been simplified to use the new filter.  Make "add_groups_to_blog" function in permission plugin into a filter that's used by xmlrpc create blog method.  Add an endpoint for xmlrpc and expose a new "create_blog" function for LTI, as well as the built-in "get_blog_details" function.