Ethereum dependency problems

[JeremyPansier]

Context
The call to POH smart contract is currently done via infura using the same key for all nodes. The infura free plan is limited to 100,000 requests a day that implies that the current implementation will reach the limit, even for a single node. In addition, The Ruthenium blockchain is currently strongly dependent on the Ethereum blockchain, because it is using an Ethereum smartcontract and it relies on Ethereum for the private key generation.

Suggestion
This limitation can be solved in several steps:

1. Ask users to provide their own infura key (see The POH smart contract calls might reach the limit #212)
2. Create an extra light Ethereum node (see Unreachable poh contract might introduce unverified blocks #141)
3. Integrate Ruthenium own POH smartcontract (see Integrate POH smart contract #213)
4. Handle private key generation (see Handle private key generation #214)