* 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
* Initial commit for CollectSignaturesFlow, some tests and associated documentation via a new "Flow Library" section of the docsite.
* Refactored the TwoPartyDealFlow to use the CollectSignaturesFlow.
* Added the subclassed CollectsigsFlow to the trader demo, whitelisted it and added a flow initiator for the responder.
* Minor edits to progress tracker.
* Amended as per Rick's comments.
* Generalised this flow, so it now works if more than one signatures have been collected, initially.
* Minor edits to the IRS demo so it uses the CollectSignaturesFlow.
* For debugging purposes...
* Adding CollectsigsFlow support to SIMM Demo.
* Removing debug logging.
* Amended top level comment: transactions can only have one notary.
* Added TODOs as checkTransaction logic is absent.
* Addressed Mike's review comments.
* Minor edit to flow-library docs.
* Updated flow based on Mike's review comments.
* Added two usage examples and updated the tests.
* Made changes to accommodate new CollectSignaturesFlow approach.
* Made changes to SIMM demo to accommodate new CollectSignaturesFlow approach.
* Added abstract check proposal method to two party deal flow.
* Added missing TODOs.
* Addressed Sham's comments.
* Rebased to M11.
