Add endpoints to forward queries to all registries

[cjmyers]

Add the following synbiohub endpoints that will query all known registries and return a combined set of results:

/sparql
/rootCollections
/remoteSearch/:query?
/search/:query?

Also consider:

/remoteLogin
/login
/logout

These later ones though may need some thought as they will only work if someone has the same credentials on all registries. It might be interesting to consider having a setup where a user can link their webOfRegistries account to each registry's corresponding user. Something like the merged "google login".