SSP-1748 - challenge_referral.link column width too small to be useful

This was a cherry-pick of 3e50df4cce1da0e051b614ec96a7e19cd98fb811.
The only conflict was in masterChangeLog.xml, which was to-be-
expected given the divergence in changelog sequencing between
master and rel-2-0-patches.

Conflicts:
	src/main/resources/org/jasig/ssp/database/masterChangeLog.xml
SSP-1748 - adjusted size of task#link to coincide with length of
challenge_referral#link..  Also added client side validation to
Challenge Referral Admin screen