Curvilinear Grid does not always renders correctly #79
Description
The first datasets which appears here:
https://gems.dkrz.de/databrowser/?start=0&variable=bfe
Has a curvilinear grid. Unfortunately, it does render the earth in an inverted way. You will only see a corona-like border, because the rest is covered by a black globe which I put underneath the texture. The issue comes directly from the function detectLongitudeFlip and if we negate the return-value, the dataset is rendered properly. However, other datasets will then not work anymore. The implementation of detectLongitudeFlip was a moving target from the beginning and we probably need another approach. Right now, however, I don't know how this is going to look like..