Statistics fixes

When attempting to use the statistics ops to verify results from other ops I was writing I noted possible errors in the statistics ops.   Thus I added a new test, StatisticsTest.java.  I also added a 'generateFloatArrayTestFunction' to AbstractOpsTest.java.

To get the new test to pass I did the following 

1.  Changed MinRealType.java and MaxRealType.java test to use copies of the 'it.next()' container.
2.  Changed MeanRealType.java op calculation to 'sum/size' (it was 'size/sum'). 

I also could not get a stddev test to pass because there were multiple signatures with the same priority.  But I wasn't sure of the best way to fix this.