Stores an object (and optionally, every object it points to recursively) in the local database.
If any of the objects have not been fetched from Parse, they will not be stored. However, if
they have changed data, the data will be retained. To get the objects back later, you can use a
ParseQuery with a cache policy that uses the local cache, or you can create an unfetched
pointer with ParseObject.createWithoutData() and then call fetchFromLocalDatastore() on it. If you modify
the object after saving it locally, such as by fetching it or saving it, those changes will
automatically be applied to the cache.
Any objects previously stored with the same key will be removed from the local database.