Add framework for using velocity templates in email classes

Setup the velocity context and add basic objects to it.  Add
a few velocity helper functions, but do not use any of it.
Allows default email templates to be in the war file and to
be overridden by placing an appropriately named template in
<site>/etc/mail.

Change-Id: I45cdbbcd19929ce52c54a5c9b8ee510b52681ed3