Make notary flow return a collection of signatures to support the BFT notary. For a single-node or RAFT notary it would just contain a single signature.
* Add support for contract upgrades
* Add interface for the upgraded contract to implement, which provides functionality for upgrading legacy states.
* Add shared upgrade command and verification code for it.
* Add DummyContractV2 to illustrate what an upgraded contract looks like.
* Add new functions to vault service to support upgrading state objects.
* Add contract upgrade flow
* Add webAddress back to NMS as it shifts the port allocation for all subsequent nodes and causes all demos to break.
* Attachment demo: fix node names
* Notary demo: fix certificate paths & ports
* IRS demo: role decider fixed to allocate roles properly. Previously it used to pick current node as the Fixer, causing both nodes to initiate the trade flow, resulting in double spend exceptions..
