Fix axis inversion on label dblclick.

My initial implementation worked. However, I overlooked that pc.flip()
already existed (so let's use that). Also, I forgot to make sure to set
the event listener in pc.updateAxes().
Add simple interaction to rotate labels.

When there are many coordinates, coordinate labels tend to overlap. To
solve this problem I added the ability to change the orientation of the
labels by means of scroll wheel interaction. Scrolling up/down on one of
the labels will cause the labels to rotate right/left.
Slightly improve readability of source code.
Make axes reorderable in brushing exampe.

This makes testing a bit easier.
Prevent a page from scrolling when using mouse wheel for label rotation.
Refine axis flipping even more.

In stead of updating all axes on an axis flip, we now just update the one
that is affected. This avoids confusing behavior which I observed when
first swapping order of axes and next flipping one.

I also removed code duplication by moving out this function into a seperate
one which is reused in createAxes and updateAxes.
Remove code duplication for label rotation similar to axes flipping.