Link nodeId (from ruleflow) to WorkItem

I would like the node ID (from the ruleflow file) to be a field of a WorkItem. It's useful to know, when handling a WorkItem in a WorkItemHandler, which node from the workflow definition is being run (particularly if the same task type is used multiple times in the workflow).

I've attached a zip file of the code changes I think are required (these files are modified versions taken from the released drools-5.1.1 source).

(I note that the id attribute for nodes in BPMN2 files is a string, so maybe a string type would be better for the nodeId field of WorkItem - in my modified source files it's a long.)