DOC: Adding missing doxygen grouping in Image documentation

Change-Id: Id55de7feefca21d0564ea23159268f88ff803758
ENH: Adding methods to Image to transfer to and from Continuous index

Change-Id: Ief943d69d564f836241de750dfd7a3314d80f16b
Remove un-used and wrong operator== in tests

Change-Id: I750e2a46859a8e8dac8dd1f3bd28d2f4fb149088
Adding testing of continuous transform methods

Change-Id: I98df48a3813a6dc1fe890a7f8ad3eed41209c67b
Merge topic 'SIMPLEITK-456_TransformContinuousIndex' into next

8f0504f7 Adding testing of continuous transform methods
b2491039 Remove un-used and wrong operator== in tests
634ab896 ENH: Adding methods to Image to transfer to and from Continuous index
db28311a DOC: Adding missing doxygen grouping in Image documentation