Localize redactor v2

This pull request supersedes #417

To be able to localize Redactor with the current `$this->requireAsset('redactor');` we need to update the redactor asset group.
So, in this pull request we have:

1. Some PRS-2 coding style fixes

2. Implemented assets de-registrations (when switching from a language to another one we have to reset the components of the redactor asset)

4. Added a `tools/i18n_redactor_js.php` file that works almost the same as `tools/i18n_js.php`. It contains localized strings and sets the redactor language to the currently active one.