typechecker: include more UserAttribute functions in reflection hhi

Summary: - added getAttributes, getAttributeRecursive, getAttributesRecursive to ReflectionClass
 - added getAttributes to ReflectionFunctionAbstract
 - added getAttributeRecursive, getAttributesRecursive to ReflectionMethod
 - included a few more return types for ReflectionFunctionAbstract

Reviewed By: @int3

Differential Revision: D1754642

Signature: t1:1754642:1419292410:9ae87bb7950305a4404be3a13068f0bd6b2cdcdc