Implement factories and repositories

Update main project to use the domain layer

Fix test errors; Update product update mechanisms to use DDD;

Update login view model to use DDD objects

Delete barcode image

Implement repositories; add tests to models and repositories

Update README.md

Move the readme file to root dir

Add readme file

Update test

Add transaction list view model tests

Add tests to stock purchase view model

Add tests to user list view model

Added tests for inventory view model

Move data templates to its own resource dictionary