Sakai Property used for debugging/testing digest emails

Digest emails are only sent one time per day. A configurable property would allow this check to be bypassed for testing purposes.

setting the new option digest.email.bypass.for.debug=true will allow the digest emails to be sent whenever they are checked for sending. When used with email.digest.check.period, you can control how often digest emails are sent. useful for testing.

attached is a patch that we developed for rSmart.