rfe12546 - added getDuplicateStatements to python API doc

Also added deleteDuplicateStatements which was defined but not
documented.

Change-Id: I25590a72d9368850a4180fd9ab97fb807b1aea44
Reviewed-on: https://gerrit.franz.com:9080/4224
Reviewed-by: Ahmon Dancy <dancy@franz.com>
Reviewed-by: John O'Rourke <jor@franz.com>
Tested-by: Kevin Layer <layer@franz.com>