Add statistics test

Additional tests for min, max, mean and stddev ops.  The tests all
follow the same pattern.

1.  Generate a random test image.  2.  Get a reference to the raw data
pointer.  3.  Calculate the statistic by directly using the raw data.
4.  Calculate the statistic by calling the op.  5.  Assert that the two
values are the same.
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.

While fixing 'Min' changed the variable name from 'max' to 'min'
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.
Merge pull request #30 from bnorthan/statistics_fixes

Statistics fixes