Ipns name resolution

This branch is not yet complete, but before i move forward, the name resolution code (in namesys) needs some critiquing. There are also a decent number of bugfixes in this branch that i ran into while trying to get the code to a point where i could test ipns.
should have: 
```Go
type ipnsPublisher struct { ... }
type Publisher interface {
  Publish(ci.PrivKey, string) error
}
```