Add iText for PDF/email support in JavaMelody

I haven't had a chance to test this yet, but the documentation is here: https://code.google.com/p/javamelody/wiki/UserGuide#14._Weekly,_daily_or_monthly_reports_by_mail

I think the "Parameters" which live in the tomcat context can also be provided as system properties, eg in standalone.xml.  We would also need to define a suitable mail session with matching name.

We can merge this either into release or integration/master.