Fix vtkSIVectorPropertyTemplate conversion

When converting return values from a client server stream into an SI
vector property, first the types must match exactly, so any previous
uint32_array instances would be rejected. In addition, support 64 bit
returns by smashing them into 32 bits.

The reason this is necessary is that the unified-bindings conversion for
tuple return values from Python uses 'long' which is 64bit on
non-Windows machines.

Change-Id: Iad162384b6642da0e7aeb58603dd0856a462316d
Merge topic 'unified-bindings2' into next

292bdc3 Fix vtkSIVectorPropertyTemplate conversion