Implementing more traits for `DeviceBox`

We should implement several additional traits for `DeviceBox<T>` to make it more useful.
- `Clone` - for duplicating data on the GPU
- `Hash` - for parallel hashing
- `Eq` and `PartialEq` - for parallel equality checking
- `AcceleratedIterator` - we should define a new trait for doing high-level iterator-based computation