Fiduswriter

Fixes:
- removes excessive data when saving equations and figures

Fixes:
- enable fidus fileupload in Firefox
- restrict fidus fileupload to *.fidus files

Fixes:
- One user edits a comments while a collaborator edits the document: wait with comment relayout until comment editing is done
- Allow to change isMajor category of comment that has been created already
- Fix error message when comment answer is updated

Main Changes:
- support for Firefox, Safari and Edge (desktop)
- replaced Mathjax with KaTeX/MathQuill
- replaced internal editing functionality with ProseMirror
- added tracking of collaborators carets
- removed tracked changes
- much increased stability

Fixes:
- Make app translations work when running on production server

The number of bugs has gone down significantly for this release.

Fixes:
- Don't throw error if user clicks on the top row of an image selection dialog
- Temporarily remove code of unfinished features (documentation system + comment rdf graph) contributed by Aleksandr Korovin (OSCOSS)

Features:
- Add initial French translation, contributed by Nicolas Rochard. Thanks!