Add function for creating several reinforcements in one go

[mortenengen]

We have the add_reinforcement function that adds one point representing one reinforcement bar at a given coordinate. We also have add_reinforcement_line and add_reinforcement_circle to simplify modelling reinforcement in rectangular and circular geometries.

It would be useful to also have a function, e.g. add_reinforcements, that behaves as add_reinforcement, but instead of providing one coordinate, we could provide a list of coordinates, and one bar is added at each coordinate.