Purpose
=======
Internal categories are only useful for accounting & inventory.
-> so they should be only visible for such modules
Also terms are confusing: internal category -> category "internal" is not obvious
Specification
=============
- remove internal categories menus from:
sales
website_sale
pos
- rename menu in:
purchase
inventory
- add menu to:
accounting
products must be visible even if account.accountant is not installed
categories only visible if account.accountant is installed
- rename categories in product form:
- category
- pos category