Refactor bridger on top of HyperDB

This is Yuge! Basically a rewrite of the bridger core-library (or almost entirely a new version) That implements two bigs changes:

1. A smart-contract registry associating ethereum addressess with hyperdb keys
2. A library for managing views onto hyperdb instances (essentially replacing "handlers")

this resolves #65 (closed) #67 (closed) #66 (closed) #6 (closed)