Form: do not validate of construction time
Validating forms on creation complicates using ChangeOps which build on
the idea of adding information step-by-step.
This was worked around so far by using BlankForm but now is further
complicated by the need to use a Form including valid FormId inside a
ChangeOp (generating statement GUIDs) - of which there is only one
stack - which creates a hen and egg problem.