Move handling of REST "expand_members" param from Rest_Controller to Rest.
Move handling of some REST resource query params from their __construct() to
their get_response().  This ensures that they're only processed for GET.
Revise comments in Rest_Items a bit.
Add Rest_Batch resource.
Make Rest_Registry return an alphabetized list.
Add members_info to base Rest class.  No resources actually populate this yet...
Add Rest::sticky_params(), revise Rest::url() & Rest::relationships() to use it.
Revise Search::search() and Search::search_within_album() - add "where" arg
which is passed to Search::_build_query_base().
Implement REST member_info["count"] for all collections, update unit tests.
Merge pull request #437 from shadlaws/fixes_20130628

Fixes 20130628