vtkPVView only passed the UseCache flag to the representations in Update
for performance reasons. Which meant there were often cases where the
representations didn't have the update state of this flag and would end
up clearing their caches unnecessarily e.g. just playing repeatedly
without looping ended up never using the cache.

To avoid this issue, we now let the representations directly access the
caching flags on the view. This resulted in a couple of backwards
incompatible changes, however, documented in MajorAPIChanges.md.

1. vtkPVDataRepresentation subclasses must call superclass AddToView and
RemoveFromView methods in their overrides.
2. vtkPVDataRepresentation::SetUseCache and
vtkPVDataRepresentation::SetCacheKey are no longer present.