TermIt

As a user, I want to be able to edit existing annotations in a document. I want to be able to: select a different term and remove the annotation.

Acceptance criteria:
- When an annotation is selected in the rendered document (e.g. by clicking on the annotated text), an annotation detail UI (probably a popup) is displayed, containing info about the annotation (already handled by a different task).
- The user is able to edit the annotation info by selecting a different term.
- The user is also able to remove the annotations.
- Server-side API to update RDFa documents
- Submitting the changes invokes server-side API for updating annotations (here only only RDFa document will be updated without update of term occurences, which will be addresed by different task).
- Tested (frontend & backend).