Add support `register_type` and `MessagePack::Factory` in JRuby

Pathes are needed to follow CRuby implementation of these features:
- `MessagePack::Factory`
- `register_type`, `registered_types` and `type_registered?` for `Packer`, `Unpacker` and `Factory`
- Many skipped specs
- Many specs to be shared with CRuby/JRuby (currently many specs are separated on cruby/jruby directory)
