NO-JIRA: Install python code as part of cmake make phase

Previosly the qpid/python code was being installed only during cmake
configuration phase and was not updated if the python code changed later.  Added
a custom target to run setup.py whenever make is run.  setup.py is smart enough
not to do un-necessary work if the python files have not changed.

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1555989 13f79535-47bb-0310-9956-ffa450edef68