Fast forward to 2.9.2

Work in progress, expecting further pull requests by Ome Jelle and Frans Cooijmans

Todo
- [ ] further clean Accented characters
- [ ] translate new lines (which were added 2.7 - 2.9)
- [ ] re-translate archaic words (geüpdatet etc.)
- [ ] translate other codeigniter lines that might be needed (form validation = done)