construct dataset from an array
test std max method against array implementation
standardization min-max for datasets
attribute builder create method now adds automatically newly created attributes to the dataset they belong to
API change: asMatrix method will provide matrix-list accessor
using dataset as matrix
addAttribute implementation
recalculation of stats
fixed dataset standardization for ArrayDataset (for other might not work right now)
fixed adding attributes
fixed creating attribute
moved stats test to its class
fixed reference to dataset in attributes
added build method to attribute builder
updated attribute factory usage
moved stats test back (because of dependency cycle)