interpolation: possibility to reclassify the data #316

Expected Behavior

for a better visualization the user should be able to reclassify the data in terms of the number of classes and the class breaks. i.e. through the choice of 2 or 3 different automatic classifiers as equal interval, qunatiles, standard deviation.

Actual Behavior

the data is classified in 5 classes and equal intervals. in many cases the visualisation makes no sense than if there are outliers in the data...