Return matching method name in ServerCodec. Fixes #24

Store the incoming method name before mangling so that it can be returned in the response.
No need to lock methodName table
Add 'Go RPC style' code generation feature.
Add command line option for enabling Go RPC style code generation.
Add Strict GO RPC code generation feature (users promise they don't
expect state to be passed via the RPC ReplyType).
ReplyType is not sent across the wire in the request. RPC service
interface can remain unchanged.
Introduce a single go.rpcstyle mode which supports Go simulated pointer
manipulation, but exposes an interface with explicit returns for general
thrift compatability.
Remove go rpc style and go strict rpc style modes.
Add factory functions for generated thrift clients and services.
Server renamed to Service in the generator.