Added all apps, fully created 'file_manager'

Added all relevant apps:
- auth
- items
- file_manager
- businesses
- documents
- shortage_table
- rates

file_manager:
- Created Image and Datasheet models
- Made an upload test for each of them

* REMARKS

- Installed reportlab and Pillow for file_manager's tests
auth, file_manager, items tests

For 'auth', 'file_manager', 'items': created/updated tests.py:
- test_create
- test_update
- test_get
- test_delete
(CRUD)

In addition - Fixed urls for item related sets (replacements, price
lines, sources etc..)