Add PoA modules, also NtoN example

[ethanfrey]

We can use a simple staking modules with a fixed set of delegators, who may delegate to different validators. Thus, the private key of the machine is not fixed, but rather the key that can assign it. This allows unwatching for example, and provides a simple module to also control dynamic testnet configurations.

All "bonds" should be indexed by both the validator and the delegator, and this provides an example of N-to-N relations and queries that needs to be modeled with the orm, for the advantage of other use cases as well.

[ethanfrey]

N to n example done.

PoA done with update validators kind of.

The story above is vague and doesn't match any business requirements.

Closing