'advanced' usersearch...

* added fullname, location, bio to dht
* added "usersearch" rpc method to search users with their name, location, etc..

It may pose some problem when user updates name, location, etc.; because we can't update multi dht resources (or i don't know how), so users will be still findable with their old infos.

But I think it's required something like this...

![usersearh](https://cloud.githubusercontent.com/assets/6997088/3300006/ac973cf6-f61b-11e3-8385-62cca571857c.png)