Bt vod synthesize hierarchy

This pull request allows to extract brands from series/episodes rows and creates brand>series>episodes hierarchies based on that. This is because brand entries are not present in the data file.
@tfm Should we fail this row if we're not able to extract a title at all (throw an exception from the final else, that is missing now...)? Note that this method is called only if this row is a brand or if it's synthesizable.