QPID-5338: Renamed the top Python package to qpiddx.

This fixes the collision between the embedded library's name and the
public Qpid Python libraries.

git-svn-id: https://svn.apache.org/repos/asf/qpid/dispatch/trunk@1541585 13f79535-47bb-0310-9956-ffa450edef68
QPID-5338: Added ChangeLog entry

git-svn-id: https://svn.apache.org/repos/asf/qpid/dispatch/trunk@1541589 13f79535-47bb-0310-9956-ffa450edef68
QPID-5335: Moved Dispatch python libraries out of public site packages.

The Python files used by Dispatch are now located in
/usr/lib/qpid-dispatch.

The path can be overridden either at compile time or at runtime.