Don't write VTK data as this writer doesn't support 2D
Only one perforation per column supported

Otherwise we would get more than one "well" per column in the upscaled
model, something which we don't support yet.
Inject CO2 instead of water in example

It is not the "Numerical Brine Laboratory"!
Merge pull request #36 from rolk/036_samp2d

Make sample be proper for 2D