Retracts all findings (i.e., the current case) from all the nodes in net, except "constant" nodes (use RetractNodeFindings_bn for that).

This includes positive findings (state and real value), negative findings, and likelihood findings.

If net does not have any findings, calling this will have no effect.

If the net is an auto-update net (see SetNetAutoUpdate_bn), then a belief updating will be done to reflect the removal of findings, before this function returns (otherwise it will just be done when needed).