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.
add:
```
// TODO(security): the PrivKey interface is currently insecure (holds the raw key). It will be secured later.
```