Rules for Bills merging and links

Added rule: allocated to stock Inventory items should be linked to Bill for such Bill creation flows as
- Bill created from the scratch
- Item Receipt + Bill
- PO -> Item Receipt ->Bill from PO
- SLT – Item Receipt – Bil
- PO-> IR -> Consignment-> Bill
- PO-> IR -> Consignment -> SO-> Invoice -> Bill
If cost was changed on Bill then in linked Inventory items the cost should be changed as well
Profit & Loss on Sale Order -> Cost details. Should be displayed Bills that are linked to Items on SO