Rationalize jQuery dialog usage

1. Use JSON to call help_text.php.
2. New function(displayDialog() to create and display a (pseudo) modal
dialog and modify modalDialog(), helpDialog() & modalNotes to call it
(provides consistent functioning). Having a non-modal dialog allows for
dialogs to be stacked.
3. New function modalConfirm replaces native confirm dialog
usage: modalConfirm(title,text).then(function (reply) {...};