Export function (and all_resources) should use iterator + buffer instead of vec

[joepio]

Currently, the all_resources function returns a Vec containing, well, all resources. That means that the maximum amount to export is coupled to the memory of the server. This effectively breaks the export command on the very cheap / lightweight instance that atomicdata.dev is running on.

The all_resources function should return an iterator, and the file writer should use a buffer.

I think @AlexMikhalev worked on this some time ago