Js add users to departments

Added functionality to add users to departments and display them:

• added actions to users controller: index, show, edit, update
• added active record relation user belongs to department (department_id column to User table, strong params)
• added ability to assign users to a department on user edit page
• shows "department assigned to" on user show page, or unassigned in case of nil.
• shows profiles on department show page of users assigned to that department.