Use of catalog to get related simulation movements from delivery lines/cells is
unreliable.

Until now, for any new code written for simulation, we often had to be careful
not to call getDeliveryRelatedValueList too early, usually by deferring code
to activities with complicated dependencies. Race conditions are difficult to
avoid by developping this way, because for a given delivery, there are
potentially so many events that happen at the same time, involving:
- simulation, amongst causality, expand, building, solving (including split)
- alarms, user actions, external interfaces, chains of activities
- several related deliveries and simulation trees

This commit enables ZODB-indexing of related documents for 'delivery' base
category, making getDeliveryRelatedValueList safe and fixing unlink of
deleted delivery lines/cells.

Existing activity dependencies are left unchanged because builders only uses
catalog and local building needs to find all simulation movements.