[ESG-1672] added own logic for is_in_stock attribute

Conflicts:
	src/app/code/community/Flagbit/MEP/Model/Export/Entity/Product.php
[FIX] Fixing product limit preventing all products to be checked in preview
[GDN-384] Changing is in stock filter on collection
[GDN-384] Improving is in stock filter
[KROTE-161] Authorizing admin store for export
Merge branch 'development' into MAGEMEP-141