Fixes for nslcm
This 2 commits make some improvements in the build script and in the overall utilization of $refs in the files.
The optimization is the following: When a $ref from a different file is used several times in a api, it's better to create a local definition where we import once from the external file and internally we refer each time to the local definition.
With this optimization the OpenAPI file built has passed from a length of 40K+ lines to a length of 25K+ lines. Several errors of references remain and further optimizations may be done, but I think it's ok to merge with the NFV-SOL005-Review branch.