Updated language translation files.

git-svn-id: https://plugins.svn.wordpress.org/wpgform/trunk@766364 b8457f37-d9ea-0310-8a92-e5e31aec5664
Added translation support for Captcha phrase.

git-svn-id: https://plugins.svn.wordpress.org/wpgform/trunk@766366 b8457f37-d9ea-0310-8a92-e5e31aec5664
Prep for v0.57 release.

git-svn-id: https://plugins.svn.wordpress.org/wpgform/trunk@766367 b8457f37-d9ea-0310-8a92-e5e31aec5664