Add generateFloatArrayTestImg

Add a new function to make a floating point test image.  The image is populated with random values.
Max and min bug fix

Changed MinRealType.java and MaxRealType.java test to use copies of the 'it.next()' container.
MeanRealType format

The auto format repositioned the opening "{" of the class to a new line.
Mean bug fix

Mean was previously calculated as size/sum.  Changed to calculate sum/size.

The mean test previously asserted that the mean of a random buffer was 15.625.  The test was changed to assert that the mean of the buffer is 1/15.625.
Addition to mean test

An additional simple "sanity check" was added to the mean test that works as follows:

1.  Populate all pixels of an image with a constant value of 100.0.
2.  Calculate the mean using the op.
3.  Assert that the mean is equal to the constant value of 100.0.