Renaming CentOS builds from cc7 to centos7 (AtlasLCG-00-00-60)

	* Changed the "short name" of CentOS to "centos" from the
	  previous "cc". As that's the new SFT convention.
	* Tagging as AtlasLCG-00-00-60

2016-06-03 Attila Krasznahorkay <Attila.Krasznahorkay@cern.ch>
	* As it turned out, the previous code broke down when trying to
	  generate environment setup files, while having included the
	  package "with version 0". This should now work as well.
	* Tagging as AtlasLCG-00-00-59

2016-06-03 Attila Krasznahorkay <Attila.Krasznahorkay@cern.ch>
	* Made it possible to make use of the modules of the package
	  without actually setting up an LCG release. So that we could use
	  the same find modules for looking up externals in standalone
	  builds as well.
	* Tagging as AtlasLCG-00-00-58


Former-commit-id: 988f487c