Bug fixes:
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* fix import tests being run multiple times  #2892
* add creative commons as a license family (used to be classified OTHER)  #2893
* handle empty packages in checks for duplicated files across subpackages  #2894
* set PYTHON and other language path vars based on presence in build/host reqs, rather than binary file in either env.  Allows usage of PYTHON and friends in meta.yaml vars.  #2895
* fix entry points incorrecty pointing at build prefix (instead of host), leading to prefix replacement failing  #2895
* fix merge_build_host functionality.  Adding an empty host section now forces build and host to be split.  #2896

Contributors:
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* @msarahan
* @scopatz