Added View error: templateName does not exist in Handlebars Templates

In the interest of easier debugging, A Mozart View should throw a specific error when the following are true:

(1) skipTemplate == false
(2) templateFunction == null / undefined
(3) window.HandlebarsTemplates[templateName]  == null / undefined

The error should be of the form 'Template #{templateName} does not exist in HandlebarsTemplates'