The template parameters on vtkm::rendering::View are unnecessary. All
three of the templated classes are polymorphic (with virtual functions).
Thus, you just have to specify them at the constructor. Removing the
template parameters makes the syntax a bit cleaner and removes some
unnecessary duplication in the executable.

Removing the template does mean we cannot optimize in the future.
However, I expect us to start using more virtual methods rather than
less, so I think this is a move in the right direction.