Add a test which make a set of transactions and perhapse post it to the polkadot implementations

[drskalman]

So it should be another julia module:

• reading from a yaml config file, decide what type of test transaction to make:
• generate the transaction (maybe using RPC interface of Substrate).
• make a transaction network message and post it to all polkadot implementation.
• verify some sort of output from them through apply_transaction perhapse.

This is very rough and needs refining but it is a start.

[FlorianFranzen]

Part of the tooling for this will be implemented with w3f/polkadot-spec#322.