[ZODB-Dev] new setup.py for ZODB4

[Jeremy Hylton]

I created a top-level setup.py for the ZODB4 package and modified the
test.py script to run tests from the build directory.  This will make
the development experience for ZODB3 and ZODB4 very similar.  The
chief advantages of this approach are:
 - Build for multiple versions of Python from a single checkout.
 - Create useful source distributions with setup.py.
 - Conditional installation of software like BDBStorage.

Jeremy