Bug 8000: (QA follow-up) Add email validation to system preferences

Bug 8000: (QA follow-up) Add email validation to system preferences

This patch uses the JQuery validator plugin to add validation to preferences of class email in the system preferences page. A field containing an invalid value (even if not modified) should prevent saving.

To test, confirm that when entering an invalid email address in the SendAllEmailsTo field, an error message appears and saving is prevented.
Correcting the value should hide the message and let you save as normal.

Signed-off-by: Liz Rea <wizzyrea@gmail.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>