Simplify code to calculate supports
Simplify code to calculate supports

The code is easier to read now, it returns the same results it used to
return, and performance-wise it's probably the same thing, but if it's
not, we'll trust Rails will do optimizations that we don't when we
manually pluck the IDs.

AyuntamientoPuertoReal/decidePuertoReal,consul/consul,AyuntamientoPuertoReal/decidePuertoReal,usabi/consul_san_borondon,usabi/consul_san_borondon,usabi/consul_san_borondon,consul/consul,consul/consul,usabi/consul_san_borondon,consul/consul,AyuntamientoPuertoReal/decidePuertoReal,consul/consul