Added Meta Box and warning message to report number of users who receive email.

git-svn-id: https://plugins.svn.wordpress.org/email-users/trunk@767401 b8457f37-d9ea-0310-8a92-e5e31aec5664
Added Dashboard Widget report number of users who receive email and default user settings.

git-svn-id: https://plugins.svn.wordpress.org/email-users/trunk@767402 b8457f37-d9ea-0310-8a92-e5e31aec5664
Prep for v4.5.2 release.

git-svn-id: https://plugins.svn.wordpress.org/email-users/trunk@767403 b8457f37-d9ea-0310-8a92-e5e31aec5664
Prep for v4.5.2 release.

git-svn-id: https://plugins.svn.wordpress.org/email-users/trunk@767404 b8457f37-d9ea-0310-8a92-e5e31aec5664