new address and manifest classes

[tabcat]

This pr will introduce and use the new classes for the Address and Manifest data types, based on https://github.com/orbitdb/SCPs/pull/12 and https://github.com/orbitdb/SCPs/pull/13.

The goal is to simplify and uniform interactions with them internally.

While integrating the classes inside this pr, OrbitDB methods returning instances of stores will be pruned to just open, as discussed with @haadcode, which will take a stringified address.