Rename/refactor? assert_dims_ok_point

[nikosbosse]

The function is used for both binary and point forecasts, so we should make that clearer in the name.

In the spirit of having code for different forecasting classes more independent (at least in terms of how the code is organised) maybe some other approach is warranted as well. Don't have strong thoughts on this yet (or any, really...)

[seabbs]

can we give it a name to make it clear the concept it is asserting and leave it at that as a utility function?