Improve perRow metric calculation

[maurever]

1. I found these changes very inefficient:

boolean score4Generic = m != null && m.getClass().toString().contains("Generic");

6421a81

We should implement something like the method isGeneric() instead of comparing the name of the class with the hardwired String.

2. I also find this condition in ModelMetricBinomial is not usefull anymore:

h2o-3/h2o-core/src/main/java/hex/ModelMetricsBinomial.java

Line 211 in 2d8671d

double err = iact + 1 < ds.length ? 1 - ds[iact + 1] : 1; // Error: distance from predicting ycls as 1.0

Because iact + 1 is always lower than ds.length for binomial cases.