COMP: Fix Multiply two images output

My previous fix did not fix the outputted image, as it is a .mha file.
I uploaded the right image for the documentation as a png to midas.
I also added the second input image to the documentation.

Change-Id: I1f7c0b83eb038a39b6736d822a9c76955f7e9662
Merge "COMP: Fix Multiply two images output"