From rich text input to PDF with overlays

- Added Dutch to the Mendix project and translated the texts in the CommunityCommons module
- Added Java action getDefaultLanguage. (Not used in the other parts of the pull request, just a useful function)
- Created AntiSamy policy files that match the functionality of the Bootstrap RTE widget. One file supports hyperlinks, the other removes them, leaving only the link text.
- Added values to the XSSPolicy enumeration to support the new policy files
- Added Java action OverlayPdfDocument.
- Replaced antisamy-1.4.4.jar with antisamy-1.5.3.jar. This was a little strange because I got the 1.5.3 version from the Mendix appstore.
- Added jars to support the new functionality
- Added testcases to the Mendix project for XSSSanitize and PDF export.

Please note that font selection is ignored by the PDF export.