Adjust tests for new interface
Add first changes on model
Add description text field as well as SKU to Part model
Adjust field definitions for Part model a little
Add test case to check Part.get_on_stock() method
Add a method _get_on_stock() to Part calculating on stock value over all StorageItems
Fix Part method below_min_stock() for STorageItem enabled handling
Rework PArt's is_on_stock() method and update test cases.

Parts, which don't have an StorageItem assigned are now marked as out of stock by this change
Merge master
Merge master
Extending test cases for external function to get all Parts with their on stock amount
Add a new global method returning a list with all Parts, their on_stock and min_stock.

It's only including the Parts having StorageItems.

This commit also redefines the testcase a little in terms of structure of expected result. Functional changes have not been implemented on that testcase.
Fix call for reordering dashboard item
Add migration file
Remove obsolete fields from PartsAddView
Update Add new transaction view to new model.

In case of no on_stock value has been defined for an storage item, just no decrement is happening.
Merge pull request #49 from frlan/feature/SKU-based-storage

Add SKU and StorageItems based basic storage mangement