Updating member access template component with const correctness

Change-Id: I3cc71d8fb12fa102bf0e5482db008b7ec805ee22
Adding const correctness to the IO module

Change-Id: I2d12feeaa13f5a588664e49eeb8c5b8cba2e8389
Updating const correctness of Get methods in BasicFilters

Change-Id: If176da950af404754071cebc571b3e1fe6be6568
Merge topic 'SIMPLEITK-452_AddConstCorrectness' into next

7b16c70 Updating const correctness of Get methods in BasicFilters
b935900 Adding const correctness to the IO module
9d0bc4a Updating member access template component with const correctness