Added support  for regular expressions as a validation check.

git-svn-id: https://plugins.svn.wordpress.org/wpgform/trunk@928911 b8457f37-d9ea-0310-8a92-e5e31aec5664
Prep for v0.70 release.

git-svn-id: https://plugins.svn.wordpress.org/wpgform/trunk@928912 b8457f37-d9ea-0310-8a92-e5e31aec5664