branch to update savepoint release changes with 1.1 release of transaction module
merge changes from elro-savepoint-release branch to current copy of trunk
transactions with rollback support

Merge remote-tracking branch 'origin/elro-savepoint-release-1.1'

Conflicts:
	CHANGES.txt
	docs/savepoint.rst
	transaction/_transaction.py
	transaction/tests/test_SampleResourceManager.py