Added support to Composer to support a model leaf of type empty.

- complete rewrite the the serialization code
- the new architecture should allow for more easily adding in validation and default value support
- properties are now written out in the order defined by the meta data (it could matter is some definitions)
- changed from using utils.resolvePath to use the lodash version
- did much manual testing and did test comparison of ping-vnfd sample with new generation

Change-Id: Ibd2bbdbdaa436b95ed19016f94425bfab4f85d8e
Signed-off-by: Bob Gallagher <bob.gallagher@riftio.com>