add test to calculate stat for Data
add basic feature transformation
check whether features are intersected in Data.__init__ rather than at __add__ step
update Data init
move feature transformators to feature class
update test for features, add datatypes - strings.
update getitem functionality after change Data.objects from matrix to array
remove commented line
update equality check
update __eq__ method for Data
use len features as dimension for objects
update getitem for data
update tests, fix slice
update __add__operation. Add matrix creation.
use nobjects and nfeatures for Data
update vif calculation: Calculate only for Linear Features.
update regression test calculation
add feature title during Add operation
add stat calculation methods to Feature classes
Merge branch 'develop' into feature/data_stat