* Moved 'ems-core' into 'nebulous' dir, and updated it from main repo.
* Add 'ems-nebulous' plugin code, the 'metric-model' specs, and a
top-level pom.xml to build everything (including EMS-Nebulous image)
* Added .gitattributes and changed EOL to LF in top-level files.
* Also adopting code to pass Zuul checks
Change-Id: Ic414a1fa382d0a9112cbc805375cf603af59cd37
