Update badges + add license

* Switch to nexus badge
* Add missing GPL license to repository.

README.md

 # FIWARE-specific documentation and Docker distribution
 
-[![FIWARE Security](https://img.shields.io/badge/FIWARE-Security-ff7059.svg?logo=data:image/png;base64,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)](https://www.fiware.org/developers/catalogue/)
-[![Documentation badge](https://readthedocs.org/projects/authzforce-ce-fiware/badge/?version=latest)](http://authzforce-ce-fiware.readthedocs.io/en/latest/?badge=latest)
+[![FIWARE Security](https://nexus.lab.fiware.org/repository/raw/public/badges/chapters/security.svg)](https://www.fiware.org/developers/catalogue/)
+[![License: GPL v3](https://img.shields.io/github/license/authzforce/fiware.svg)](https://www.gnu.org/licenses/gpl-3.0)
 [![](https://img.shields.io/badge/tag-authzforce-orange.svg?logo=stackoverflow)](http://stackoverflow.com/questions/tagged/authzforce)
 [![Support badge]( https://img.shields.io/badge/support-ask.fiware.org-yellowgreen.svg)](https://ask.fiware.org/questions/scope:all/sort:activity-desc/tags:authzforce/)
+<br>
+[![Documentation badge](https://readthedocs.org/projects/authzforce-ce-fiware/badge/?version=latest)](http://authzforce-ce-fiware.readthedocs.io/en/latest/?badge=latest)
 
 This project is part of [FIWARE](https://www.fiware.org). More info on the [FIWARE catalogue](http://catalogue.fiware.org/enablers/authorization-pdp-authzforce).