Bugfix: Added missing requires to the plugin code
several cosmetic changes

- Moved the page management block to the bottom of the page, as editing should be the default behaviour
- Consistent use of $opts['rp_nr'] instead of $opts['nr'] and $opts['rp_nr']
- Added hyperlinks to the pages mentioned in success and error messages
- Clarified some of the error messages
- Updated the dutch translation files to reflect the changes in the english translations
Feature: Added updated forward links and backlinks to case modification
Merge pull request #8 from Scharrels/master

Support for backlinks