Setup quantity unit on tax.

Also allow to tax everything.

Users has no possibility to pay.

Users has no possibility to pay for now.

For example Trade Model Rules do not define trade phase on them, so let other
checks to apply it or not.

So there is no need to require it on line.

Fix condition name.

Not all Open Sale Orders have lines, but all have to be migrated.

Arrow and usual categories are set on Open Sale Order.

Let the cluster take decision about how activities will be running.

Sale Order and Sale Packing Lists can have uncommon, migration related specialise.

Invoice shall have only correct specialise.

Share and improve common logic: if Business Process does not provide links for
rule's trade phase do not apply.