added _make_2d to IpolBase in order to make passing single datasets into the __call__ methods easier. Adjusted OrdinaryKriging's __call__ method accordingly.
added _make_2d to IpolBase in order to make passing single datasets into the __call__ methods easier.
Adjusted OrdinaryKriging's __call__ method accordingly.

--HG--
branch : feature/tp/kriging

heistermann/wradlib,wradlib/wradlib,kmuehlbauer/wradlib,heistermann/wradlib,wradlib/wradlib,kmuehlbauer/wradlib