Add stakepooluserinfo and addticket RPC handling

[cjepson]

JSON handling for two new legacy RPC functions designed to aid wallets
running stake pools, stakepooluserinfo and addticket, have been added.

[chappjc]

I mentioned in IRC a week or so ago that I accidentally purchased a ticket from a wallet with no pub addr registered with the pool, but using a pool ticket address obtained with a different registered wallet. Is this commit for something like that where there is now a stray ticket, or is that handled already?

[cjepson]

@chappjc addticket will let you jam in a ticket into the stake manager in the case the user submits a bad ticket but your pool owns the voting rights for the ticket. For example it might have had the wrong fee, etc. This is just in case a user messes up on mainnet once or twice but is otherwise a contributing member of the pool. You can also use it to force in tickets to your pool without fees, if you want to allow yourself or other people to not pay fees. These manually tickets do not show up in the stakepooluserinfo except maybe as invalids.

[alexlyp]

tACK