Design issue around template kwargs

[RobinPicard]

Following the PR #1576, template variable arguments must be provided within a dictionary when using an Application (because kwargs are reserved for the inference parameters). An issue is that when using a Template directly, then you must kwargs. It's a bit confusing to use different argument types to do the same thing (rendering a template).

On top of this specific case, there may be a more general design problem with kwargs used for different things colliding with each others.