Added support for preset form values on Wordpress URL.

git-svn-id: https://plugins.svn.wordpress.org/wpgform/trunk@795291 b8457f37-d9ea-0310-8a92-e5e31aec5664
Prep for v0.59 release.

git-svn-id: https://plugins.svn.wordpress.org/wpgform/trunk@795292 b8457f37-d9ea-0310-8a92-e5e31aec5664