Feature/gridconstruction without ug

I do not see a reason to restrict the createSphere.hh functionality to UGGrid users. I propose to stick to calling the factory as given by the GridFactory interface which immediately makes it accessible to all grids alike.

Note: This changes the interface of the makeSphere function which is why I created a feature branch instead of pushing it directly. It no longer takes a grid as input and one needs to specify the grid type explicitly when using the function.

Plan: I intend to merge this feature on 2017-05-10 unless concern or dissent is raised.