Remove binsize argument from gridded_skill

[ecomodeller]

The previous implementation missed parts of the data.

This PR removes this argument.

More explicit control over bins, use the bins argument with a list of bins.

[jsmariegaard]

I can't really make up my mind about this. Somehow I would like it to be like hist etc where you just have a single argument bins which can be different things. But most times you would actually want to specify just the binsize (which should be the same in x and y direction) e.g. 2 degrees formatted nicely so not -3.3, -1.3, 0.7, ... etc but -4, -2, 0, 2, ... The user can of course do this on their own...

[ecomodeller]

I can't really make up my mind about this. Somehow I would like it to be like hist etc where you just have a single argument bins which can be different things. But most times you would actually want to specify just the binsize (which should be the same in x and y direction) e.g. 2 degrees formatted nicely so not -3.3, -1.3, 0.7, ... etc but -4, -2, 0, 2, ... The user can of course do this on their own...

Sure, but in any case, they want the entire domain to be covered. Not skip some part to the right and the top...