Should we add the other Drosophilid registrations and surfaces directly to this package?

[jdmanton]

We could use the new git repository features to download the registrations instead, but there's currently no support (as far as I am aware) for downloading surface data. Would it be best to add the latter instead?

[jefferis]

I think we should add the surfaces and template objects directly. But adding all the registrations starts to get a bit heavy, so I think we should omit those.

[jefferis]

We should also ensure that docs for fetching additional registrations are OK.