* WIP - Removed data Vending services, fixed all flow test
* * separated out extra data, extra data are sent after the SendTransactionFlow if required
* New SendProposalFlow for sending TradeProposal, which contains StateAndRef.
* WIP
* * removed TradeProposal interface.
* changed SendProposalFlow to SendStateAndRefFlow, same for receive side.
* fixup after rebase.
* * undo changes in .idea folder
* * remove unintended changes
* * Addressed PR issues
* * doc changes
* * addressed pr issues
* moved ResolveTransactionsFlow to internal
* changed FlowLogic<Unit> to FlowLogic<Void?> for java use case
* * addressed PR issues
* renamed DataVendingFlow in TestUtill to TestDataVendingFlow to avoid name confusion, and moved it to core/test
* * removed reference to ResolveTransactionsFlow
