Introduce ObjectConvertor for conversion to known API versions

Will allow clients to transform internal objects to a version
suitable for external output.
Introduce ObjectConvertor for conversion to known API versions

Will allow clients to transform internal objects to a version
suitable for external output.
Add Object type to runtime, make runtime test pass.

Conflicts:
	pkg/api/v1beta1/conversion.go
	pkg/runtime/helper.go
	pkg/runtime/object_test.go
	pkg/runtime/types.go