Allow parameter to specify the filename for "the main template" about arm-ttk

[bmoore-msft]

Fixed via #261

[bmoore-msft]

This is intentional... the scenario is this:

If the file is the top level deployment template, then it's permissible to provide a defaultValue on the location parameter. If the file is a nested template, then the value of location must be passed through. If there is a defaultValue, then it's easy to forget to pass the value through. We check on the nested template (instead of the invocation of the template in the deployments resource) because it's much easier.

Now re: the naming... it's conceivable to have a param that indicates the name of mainTemplate - so if your "top level template" is called foo.json, you could pass something to the tests to indicate that you don't have a mainTemplate.json (for example) but it's called "foo.json".

If that sounds right to you, we can change the title of this issue to reflect that...

[JFolberth]

That sounds potentially good to me.