Add semantics of `ticket`s

[sskeirik]

Several subtasks:

• extend the type syntax to include ticket
• add the constructors for tickets to the value syntax (i.e. the Data sort)
• add the instruction syntax for instructions relating to tickets
• add the semantics of the instructions for tickets
• add unit tests for ticket instructions
• mark the unit tests failing for the cross validation test harness (because our pinned tezos version doesn't support tickets)