move code for loading template config to a common helper

[joachim-n]

loadTemplateIndex() and loadTemplateView() have common code with the following logic:

• does the plugin module provide a template for the ID of the thing we want to create?
  -- if so, load that
  -- if not, load the template from the Finders module

That should be in a common helper -- it's quite possible that we'll need this for other things.