Redirect to a "good" page if URL is not known to zanata

Description of problem:
If a url is used that is not valid, it results in either a JBWEBxxxx http 404 error, or an exception.
The home page should be shown, with a notification of the bad page or something. Or even a special 404 page saying oops.

Version-Release number of selected component (if applicable):
3.5

How reproducible:
Easy always

Steps to Reproduce:
1. Go to $server/zanata/notarealpage

Actual results:
JBoss error page

Expected results:
Better page

Additional info: