First stab at implementing finaliser tasks. Dependencies of finaliser tasks are for now ignored.
Also handle dependencies of finaliser tasks
Make build dashboard task a finaliser for reporting tasks
Run finaliser tasks as soon as possible
Mock a task method to fix some tests
Docs for finaliser task and the missing setter for finalisedBy
Fix setter for finalisedBy and add a test for it.
Use US spelling for 'finalize'
Add finalizedBy edges to task graph so that finalizer dependencies are traversed only once
More extensive integration tests for finalizer tasks