[feature-request] generalize the wrap and deg2rad functions for half-circular feature spaces (e.g. bar orientations)

[GidonFrischkorn]

In some visual WM tasks participants are asked to remember the orientation of a bar. This feature space does only encompass a half-circle and thus we would have to adapt some of the helper function for the circular model. The user could just multiply the deviation in degrees with 2 and thereby rescale the feature space to a full-circle, but I wonder if we could handle that more elegantly with some of the helper function implemented in the package.

The other option would be to add some information in the article on continuous reproduction tasks that explains how to treat half-circular feature spaces when using the respective bmmodels

What do you think @venpopov?