Create new Facilities cell for GymDetailViewController

[ywsang]

Create a new UICollectionViewCell to replace the current GymDetailFacilitiesCell.
This cell should contain a "FACILITIES" label and a collection view that contains DropdownViewCells. The DropdownViewCells should be generic so that they can be configured for any facility. This requires that DropdownView is modified to have a UICollectionView as its contentView that takes in an array of detailTypes as its data source.