Added screen that allows a user to manage a list of Customers.

• Customer should have a Name and a Type,
• Frontend Name is required and must have a minimum length of 5 characters,
• Backend Name is required and must have a minimum length of 5 characters,
• Type is required and should be a select box of either "Large" or "Small",
• There should be a form to add a new customer (like on the jobs page,
• There should be a list to see all the customers (like on the jobs page),
• There should be a link on the list to open the customer record (like on the jobs page).

Extended job page:

• Allow assigning a job to a customer,
• When creating a job the user should be able to pick a customer from the dropdown,
• Frontend Selecting a customer should be required for creating a job,
• Backend Selecting a customer should be required for creating a job,
• The user should be able to see assigned customer in the jobs list,
• For any existing jobs that were not assigned to a customer it should display "Unknown" in the list,
• When the user opens the job details from the list this screen should include information about the Customer - Name and Type.