Allow multiple decisions to be returned from the brancher

[ImkoMarijnissen]

Currently, the brancher only allows a single decision to be returned.

However, it could be useful to allow the brancher to make multiple decisions at the same time (i.e. if a brancher makes multiple decisions and does not want/require propagation in between the decisions). The easiest way to do this would be to return a vector from the decisions returned by the brancher