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.
Lines 24-33 are probably repeated in a couple places in the codebase. Maybe worth writing a `func (ci.PrivKey) GetPublicKeyHash()` or something.