Validation for "Account number" must be unique for organization

Purpose/Overview: 

User must be made aware that Organizations can not have duplicate account numbers. Rather than use a migration script we will add validation to prompt users to make corrections themselves if they have any orgs with duplicate account numbers

Scenario:

1. Validate in edit form
   • Given user is editing organization
   • When org has duplicate account number
   • Then ui highlights fields and displays message: "An organization can not have duplicate account numbers"
2. Validate on add interface, contact, integration
   • Given user is adding interface, contact or integration
   • When org has duplicate account number
   • Then ui throws error message: "An organization can not have duplicate account numbers"
3. Display warning banner
   • Given user is viewing organization
   • When that org has duplicate account numbers
   • Then warning banner displays at top of view pane with message: "An organization can not have duplicate account numbers. Before editing this organization in any way you will need to change or remove any duplicate account numbers"

Acceptance criteria:

• Validation updated
• Tests updated