Allow GridField / ModelAdmin panels to have their own templates

I have some panels where just the Title isn't good enough. With contact for submissions I also want to see the date of the submission.

Updated the two panels to check and use a custom template if there is one. Since the template name uses elements from the config it means the panels can have their own templates.

Updated the methods which get the items so the whole object is passed back to the template - with the EditLink added to the object so that can still be used.

Removed the screen shot from the README as github didn't like it.