Use milestoneable to find/create a milestone
Use milestoneable to find/create a milestone

This way we simplify the code and avoid strange cases like `params[:id]`
having an ID which doesn't belong to the current milestoneable.

AjuntamentdeCastello/consul,usabi/consul_san_borondon,usabi/consul_san_borondon,AyuntamientoPuertoReal/decidePuertoReal,consul/consul,consul/consul,AyuntamientoMadrid/participacion,AyuntamientoMadrid/participacion,consul/consul,AjuntamentdeCastello/consul,AyuntamientoMadrid/participacion,AyuntamientoPuertoReal/decidePuertoReal,consul/consul,AjuntamentdeCastello/consul,usabi/consul_san_borondon,consul/consul,AyuntamientoPuertoReal/decidePuertoReal,usabi/consul_san_borondon,AyuntamientoMadrid/participacion,AjuntamentdeCastello/consul