Payment related categories shall be setup on Payment Transaction Lines, as they
correspond proper Bank Account.

Specialise can vary, so it is better to have it on lines too.

It is too early, as started or later invoices shall be considered as completed
(from accounting transaction point of view).

So it have to be setup on accounting lines.

It is required by accounting_workflow scripts.

Just add not present yet causalities.

Invoice comes from many causalities which are added continously.

Make invoice multispecialised.

Store not so important categories on movements instead of on invoice itself.

BUGFIX. Fix function used to find Slave Instance related with Software Instance that will be destroyed. When the state of Slave Instance was stopped, this object was ignored. Now, all states are considered to destroy

Nothing shall be delivered in this moment. Only top level Simulation Movements
shall be buildable.

During development document can be added to this list.

Invoice can gather movements with many dates.