Cleanups to RPC code.
Ticket issuing (RIPD-368):
* New CreateTicket transactor to create tickets
* New CancelTicket transactor to cancel tickets
* Ledger entries for tickets & associated functions
* First draft of M-of-N documentation
Ticket integration tests
Cleanups (RIPD-532)
Handle whitespace separating an 'ip port' correctly
Refactor LedgerEntrySet:
* Split adjustOwnerCount to increment and decrement paths.
* Move pathfinding-specific functions out of LedgerEntrySet
* Convert members to free functions