ENH: making old ImageRegionSplitter compatible with new splitter

Derive ImageRegionSplitter from new ImageRegionSplitterBase.

Make new templess methods call old templeted methods of
ImageRegionSplitter so that the old splitters could be used where the
new interface is expected.

Update StreamingImageFilter to take the use the new
ImageRegionSplitterBase.

Change-Id: I392c9221e6f91d685f366ce9405fb98040b24b66
Merge topic 'ConsolidateImageRegionSplittingp1'

d84ddc8 ENH: making old ImageRegionSplitter compatible with new splitter