Price grouping should use rounding

It allows to group all invoice line related to the same resource

Some software instances has no open sale order line related.

It will allow to index not instantiated Software Instances.

It is required to try harder to find root hosting subscription, especially
during upgrades.

Users are locked until they will registration payment, as soon as related
invoice is stopped.

It was generating incorrect payment transactions.

This is script for payable, so in case of receivable its value have to be
negated.

This is for payable, not receivable part.

Positive balance on this account means, that mirror_section_uid "owns" money to
section_uid.