The AntiFeatures metadata is a comma-separated list of tags, like
Categories, so it should also be stored internally as a list. This makes
parsing XML and JSON easier.
The test cases' .pickle files look like they change a lot, but they really
don't, its only the change of default AntiFeatures value from None to []
The .pickle was created by dumping the output from parsing the current .txt
metadata for org.adaway. The JSON started from that pickle dump, but was
then hand edited to be more proper JSON, e.g. using boolean values.
