Add support for a sample transaction dapp

[arcolife]

An example is that of bank.py under https://github.com/truechain/py-trueconsensus/blob/master/trueconsensus/dapps/bank.py

which gives something to this consensus to execute, as a PoC for payload execution, in future, with Truechain Virtual Machine (~EVM)

At the moment, the codebase doesn't execute anything

func (nd *Node) execute(am ApplyMsg) {
    // TODO: add msg to applyCh, should be executed in a separate go routine
    // TODO: add we probably want to keep a log for this
    nd.applyCh <- am
}