Merge resolver into c2s

Ref. #109

Pros:
* no more "remote" authentication
* presence can be looked up immediately
* no race conditions/sync issues between c2s and resolver
* much easier presence takeover and load balancing

Cons:
* no more resolver route (backwards incompatibility)
* domain kontalk.net will be handled by c2s
* much bigger and complex component (despite, modularization can help)

Tasks currently delegated to the resolver:
- [x] network domain route resolution
- [x] fingerprint verification for login
- [x] vCard requests/public key storage
- [x] presence data cache (use external key/value database?)
- [x] presence data/public key network broadcast
- [x] stanza authorization