allow explicit service name for resources

allow for explicitly named services created implicitly for resources.  before 0.14 (244905247876b) the routes registered for services were named using the services' path.  in newer versions they're named using the services' name, though, thereby potentially breaking old code.

for example, we were using constants to register the services and then use to generate urls (via `route_url`).  changing all occurrences of these would be rather cumbersome.  with this patch only the service definitions need to be changed...

note that this also contains 212462ec6ef5ddeab8fbd84e220b4b97d0b27974 as https://github.com/mozilla-services/cornice/pull/164 hasn't been merged yet.