Documentation: AssignmentMapping

[TobyUCL]

It would be clearer if the documentation specified the datatype of pred_loc, ref_loc and pred_prob. I initially thought pred_loc meant the location of the file containing the prediction and that the network was going to read the file. pred_loc is actually an array.

https://github.com/csudre/MetricsReloaded/blob/160de53fc57a64ad6c0eb6bc07e12ef11e537b0e/utility/assignment_localization.py#L13-L15