Revert "re-add plone.supermodel and plone.registry -- jenkins build for py26 did not pull commit https://github.com/plone/plone.registry/commit/80d7763842e8c49865f7f22c31d64257e7b8adb1 automatically, which fixes regression that was caused in https://github.com/plone/buildout.coredev/commit/6f8b2172c21094f9c59a27db163cbc9382c393bf -- this commit hopefully triggers jenkins build that actually pulls in the fix."  Previous fix was insufficient, will try this again.

This reverts commit b191a51c264c9405705e062fccbd8f00864da150.