Substrate Wrapper - Retrieve nonce and other data from RPC when submitting extrinsic

[willemolding]

Currently the API for submitting extrinsics via the Substrate wrapper uses the same input data structure as the Substrate signing API. That is it requires passing every value required to build an extrinsic.

The API consumer needs to separately make calls to other exposed methods (e.g. getNonceForAccount, genesisHash) in order to get the data needed to call signAndSend. Since this is such a common operation it could be made much more streamlined if the API for signAndSend accepted only data that cannot be automatically filled (call, tip, sender, etc) and internally makes the calls to populate the remainder. This is much more similar to the experience of using the Polkadot-js API

The public API of the wrapper should be changed to reflect the above and the internal logic updated to automatically make the required RPC calls.