Internal links to documents whose name contains spaces are not handled correctly.

In the ECM its possible to create documents with spaces in the name. In the repository those space are replaced by x0020, in the URL of the HST application by '+'. Internal links to those documents use whitespace, and ommit the .html extension.
IOW, they do not seem to get rewritten.

To reproduce:
0] Build & run the HST gettingstarted apps
1] Edit a document (intro will do)
2] Create two internal links to 'pagecontent/Products/Hippo CMS' & 'pagecontent/Products/Products.html'
3] Compare the two links in the sample site

Expected behaviour:
link1: /preview/page/content/pagecontent/Products/Hippo+CMS.html
link2: /preview/page/content/pagecontent/Products/Products.html

Actual behaviour:
link1: /preview/Hippo CMS
link2: /preview/page/content/pagecontent/Products/Products.html (correct)