Pro version: Add a way to change the page heading.

git-svn-id: https://plugins.svn.wordpress.org/admin-menu-editor/trunk@874038 b8457f37-d9ea-0310-8a92-e5e31aec5664
Fix edit field height. It should be an integer, not a fractional number. Also adjust the margin so that the total height is about the same, but the content height is slightly larger.

git-svn-id: https://plugins.svn.wordpress.org/admin-menu-editor/trunk@874041 b8457f37-d9ea-0310-8a92-e5e31aec5664