Refactor harvest pipeline

[fako]

• [x] Allow management of targets through the admin interface
• [x] Merge the API harvest and extract steps, where everything should go through the download and Tika steps
• [x] Merge the video download and transcription steps
• [x] Rewrite IMSCP dump to only use Tika resources
• [x] Split arrangements into their html and video counterparts during Freeze
• [x] Check other meta data like licenses and education level