Another JS helloworld. Nothing special.

• User should be able to see a list on contacts.
• User should be able to read selected contact information.
• User should be able to add new contact.
• User should be able to edit existing contact.
• User should be able to remove existing contact.
• User should be able to select multiple contacts.
• User should be able to remove multiple contacts.
• User should be able to search by firstname/lastname through the contacts.
• User should be able to group contacts.
• User should be able to search by group through the contacts.
• User should be able to put an existing contact inside one existing group.
• User should be able to change the contact's group.

• Vanilla Javascript on the client-side.
• UI is not needed.