PerpendicularDirSelector doesn't work with curved surfaces

I had some issues with PerpendicularDirSelector and from a bit of digging found it is currently limited to faces of type `PLANE` only. I was trying to select gear teeth surfaces which are perpendicular Z but are splines and so are not selected.

It's limited in BaseDirSelector `if isinstance(o, Face) and o.geomType() == "PLANE":` with the comment:

> a face is only parallel to a direction if it is a plane, and its normal is parallel to the dir

which isn't really relevant to checking perpendicularity.

I think this is left over from the original implementation that assumed perpendicular = not parallel (so all direction selectors worked from this base parallel check), but this was fixed in #882. It works as expected if I remove ` and o.geomType() == "PLANE"`:

I assume all faces have a normal defined so can't see an issue with this, but I don't know if there are other reasons to keep this check? Happy to open a PR if this can be done!

Minimum example to test:
```
p = (cq.Workplane('XY')
.circle(10)
.extrude(20)
.faces('#Z')
)
print(p.vals()) # -> []
# Should include the cylindrical surface
```

(gears created with [cq_gears](https://github.com/meadiode/cq_gears) plugin)