Some many2one fields must be displayed as widget="selection"

The following many2one fields must be set as widget="selection" in the related form views:
- Partners: customer location, supplier location, fiscal position, payment term
- Sale Order: shop, fiscal position, payment term
- Purchase Order: warehouse, desitionation location, fiscal position
- Task: type
- Employee: Category, Company
- Analytic Account: Company, Reinvoice Costs
- Products: Procurement, Production & Inventory Locations
    - put a domain on each of these 3 fields on the type of location: procurement, production, inventory
- All CRM Cases views (opportunities, meetings, ...): section_id

On all objects:
- company_id field where it exists