Remove broken quota-classes API

It turns out os-quota-classes-sets never worked
(http://lists.openstack.org/pipermail/openstack-dev/2014-February/027574.html). Since this doesn't work no need to keep it around.

V3 removal: Id1f288baa723df825151bd84aa27089271c2b8e4
Original commit: I6b6477481187d16af225d33c1989430e4071d5a8

This patch just removes the API it doesn't remove the quota-class
internals, that will be done in a subsequent patch.

Change-Id: I1110022d6f628d03aaf363da707f2d2ef1600437
Merge "Remove broken quota-classes API"