Properties files are encoded in UTF-8 but read in ISO-8859-1

All properties files are encoded in UTF-8, but they are read in ISO-8859-1. So when accents are written in properties files, they are not shown properly in web pages.

This is the default behaviour of Java: http://download.oracle.com/javase/1.5.0/docs/api/java/util/Properties.html
This is a problem known with Wicket 1.4: https://issues.apache.org/jira/browse/WICKET-2451

The trick is to write accents with HTML entities, but this is quite annoying (error prone, makes translation more complex, prevents the use of a spell-checker) and restrictive (labels can only be used in HTML scope).