Fix inventory

NEW Add option SITUATION_DISPLAY_DIFF_ON_PDF to display progress or difference for situation invoices

possible keys

FIX: fix params order for the addline() function

NEW : Add module resources import/export

NEW Add hook into subscriptions

- Move all needed declaration from coreobject to commonobject for
updateCommon, fetchCommon, deleteCommon, createCommon
- Just leave method for child object into coreobject, check later if is
useless
- debug inventory card, PHP 7.0 compatibility
- activate rights for inventory into stock module
- add inventory options into stock admin module

is automatically created. This save one click into invoice workflow.