Bug fix: do not register guest customers when their order is only PENDING. Check for duplicate email address before inserting user, in case guest email is in use by different user. Check for rare case in which another user with a different email address may be using this guest customer email address only as a user login. Delete option upon plugin deactivation. Updated .pot file.

git-svn-id: http://plugins.svn.wordpress.org/edd-cf7-register-guest-customers/trunk@850987 b8457f37-d9ea-0310-8a92-e5e31aec5664