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.
Ah good call! maybe we should implement the caching with an LRU datastore-- i made one recently https://github.com/jbenet/datastore.go/blob/master/lru/datastore.go