* Define SubscriptionManager and instantiate in generated wrappers
* expose subscribe/unsubscribe in generated wrappers
* update changelogs
* use SubscriptionManager in `@0x/contract-wrappers`
* Export artifacts and addresses from abi-gen-wrappers
* only export addresses, not artifacts
* abi-gen-wrappers no longer accept ContractAbi as constructor param
ABI is now hardcoded when wrapper is generated
* remove unused imports
* remove unused import
* changes after review
* fix method ordering
* update constructor args
* prettier
* statically enumerate ABI properties
* remove abi-gen-wrappers generated-wrappers from prettierignore
* add template for recursive components
* add `indexed` field for EventParameter
* prettier
* update known-good wrappers with ABIs and fix Python ABI loading
* remove generated-artifacts and update gitignore