Closes #18

Closes #17

* Added conversion plugins (API might change!)
* Added conversion to the analysis pipeline
* Changed behaviour of --default-plugins (it adds conversion plugins regardless)
* Added emotionModel [sic] and emotionConversion models

//TODO add conversion tests
//TODO add conversion to docs

This allows for better framing when two entries have the same @id

Also:
 * Shelve -> Pickle to avoid weird db problems
 * Serving schemas and contexts

There are also some slight changes to the JSON schemas and the use of
JSON-LD.