[WIP] Router sharding proposal

Ok.  I will leave the wildcard examples and note that if the user owns their own domain they are responsible for pointing it to the allocated shard themselves.  System provided dns (`ns-host.shard1.v3.rhcloud.com`) will work with no extra runtime config changes.  

Adding shards would be part of the dns plugin implementation in conjunction with the admin api to register the shard with the scheduler the same way as adding a router works with the scheduler and router plugin.

One thing to note, users can still take advantage of our DNS RR implementation with their own domain if they setup a CNAME record that points to their allocated shard (`www.myapp.com -> shard1.v3.rhcloud.com -> router 1 | router 2`)