Feature/the break up

- [x] Move UICollectionViewDelegate implementation from MBContactPicker to ContactCollectionView
- [x] Move UICollectionViewFlowlayoutDelegate implementation from MBContactPicker to ContactCollectionView
- [x] Move UICollectionViewDataSource implementation from MBContactPicker to ContactCollectionView
- [x] Move UITextFieldDelegate to the collection view as it's just concerned with backspaces, leave UIControlEventEditingChanged delegate intact