Changes to Elda's error reporting. In general
Elda throws a limited variety of exceptions through RouterRestlet, expecting
them to me managed by the container within which it sits. Specifically we
design for Tomcat and have error-page declarations in the web.xml which map
these exceptions to some default text with no details (hence not leaking
details to a possible attacker).

Tomcat allows those default pages to be overridden by setting Context's
in the conf directories, allowing the error dsiaplyas to be styled as
appropriate to the application.