Better http responses for CustomerController in Service API

Description

CustomerController does not fully conform to expected REST API responses. See Microsoft REST API guidelines for more info.

For example:
In GetContact(Guid contactId) of CustomerController, an OK 200 response is always returned even if the contact is not found.
In GetOrganization(string orgId) of CustomerController, an OK 200 response is always returned even if the organization is not found.

Should return not found in those cases.