Make contract wrappers easier to work with.

[jalextowle]

There are two main areas in which our contract wrappers could be improved:

(1) We should have the ability to manually generate contract wrappers (and maybe we do). There are lots of missing contract wrappers in ethereum/wrappers, and this list will only get larger as more smart contracts are added to the monorepo. This makes it very desirable to write tests in Typescript (a language that has excellent contract wrapper support), but this is not always a good fit (and should not be used as a crutch for tests that will be run frequently and take a long time to execute). (2) We should support an awaitTransactionSuccess function on contract wrappers like the Typescript contract wrappers do. This would clean up the code a lot and fix some common race conditions, and if integrated with syncWithLatestBlock (this may or may be a good idea) would fix even more race conditions.