SpendingProposal

Is this spending proposal accepted? Accepted means that this wallet has "oked" it. But it might not be ready yet. call accept() to set 0 if not accepted, otherwise millinow at the time of acceptance

Automatically post the completed transaction to the blockchain when completed

Derived class sets to millinow when this spending proposal contains enough information to actually spend

Wallet sets to millinow when this completed proposal's transaction is seen in tx pools.

Is this spending proposal valid? call invalidate() to assign to false

You need to override this function to actually do what should be done after acceptance. Set completed to millinow once the proposal is complete. This does not need to happen right away. There may be other steps (such as other wallet's acceptances) needed before a proposal can be completed. On startup, this function will be called again for every accepted-but-not-completed proposal.