This allows both tspend and treasury policies to be set by clients on a per-ticket basis. Preferences can be set when initially registering a ticket with `/payfee`, and can be later updated using `/setvotechoices`.
Any requests which alter treasury/tspend policy will be stored in the database using the existing accountability system.
**Note:** This does not include consistency checking, it will need to be added later when dcrwallet has an RPC to retrieve policies in batches.
**NOTE: This contains a backwards incompatible database migration, so if you plan to test it, please make a copy of your database first.**
Moves tickets from a single database bucket containing JSON encoded strings, to a bucket for each ticket.
This change is to preemptively deal with scaling issues seen with databases containing tens of thousands of tickets.
