Fix formNavigate to work with multiple forms & ajax

The formNavigate.js does not work reliably with the following:

• forms with ajax-loaded content
• popup forms
• tabbed forms
• multiple forms on the same page

It also doesn't do a good job of tracking changes and often gives false-positive warnings.

Steps to fix;

• Migrate tpl include to a form class variable
• Update core form renderer to add variable to markup
• Add function to CRM.utils (Common.js) to detect form changes
• Add global crmLoad event listener to store initial state of form elements
• Add global onBeforeUnload handler to check for unsaved changes

reference: http://dustinmartin.net/monitoring-a-form-for-changes-with-jquery/