Merge pull request #159 from wardi/master

Dataset form: add license drop-down, and add required static licenses.json file
Merge pull request #160 from wardi/master

navl schema: allow apostrophe in keywords, fix: tag vocabs were stored as extras as well as tags
test: start testing trim_package function used for replacing with load-datasets
test: treat empty strings as no tags for tag vocabs
fix: treat empty strings as no tags for tag vocabs
fix: handle urls with whitespace (seem to get stripped in db)