Add Any and SemiAny reps
Add Any and SemiAny reps

Summary:
Unlike the conformance/if/any.thirft, this Any can represent any value, including unions, primitive types, etc.
wrapper and tests to follow (along with a type registry, etc)

Reviewed By: Mizuchi

Differential Revision: D35837828

fbshipit-source-id: 49f37b44eb77d98b90d1dc3cbc645d0a76d79c87

facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift