Spike for a new API for declaring endpoints

@amagdas there is this [hipchat](https://sourcefabric.hipchat.com/chat) where it's kind of lonely..
in this case it's useful to have some code in place to talk about it. that's what PRs are for anyhow. so having `init_app` interface is good for reusing apps out of superdesk. we could have some other means for internal usage but not sure if we need it