Review the trash section of the upgrade notes

Problem: the section starts with explaining how to do for keeping the old way of dealing with trash, which is not very logical since even when wanting to use the new system there are things to do. even more confusing, the "new system" instructions embeds/ refer to the keeping the old system, so we kind of get lost. 

Proposed Solution
We should consider the reader is willing to use the new system and thus give him directly the mendatory instructions to perform the data migration, in a directive way (versus currently: If you want to migrate trash state to the new property model ....) and explain that all queries have to be updated. Then we can have a  "if you want to stay on old system for some reasons like not wanting to update your queries yet .... do ...”