Create new Facilities cell for GymDetailViewController

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.