Add "Are You Sure" plug in to Identify page

Look out for unsaved changes in Identify step before moving to the next step.

This uses the jQuery Are You Sure plugin: https://github.com/codedance/jquery.AreYouSure

Also includes a 'cleanup' of the `identify.ftl` where the <form> tag was not closed, and a way of showing works which do not have titles (show the object id instead).