Export state for zero height

[alpe]

With a zero height export the genesis would be exported with a state that allows to launch a new chain with a new validator set. This can be very useful for recovering or to setup testnets that are based on some production data.

To achieve this all in flight data and state that relates to validators need to be cleaned up. For example unclaimed rewards or unbonded state should be claimed automatically. The cosmos-sdk code is a good resource to start looking at. Although for us this needs to go into PoE and contracts.

This was descoped from #50