Add support for drone storage (FTP)

[Mechazawa]

Add support for fetching images from the drone's storage.

[vvo]

Again, any pointers so I can help you maybe?

[Mechazawa]

I haven't looked into it that much but from what I can tell there are two BLE characteristics that you can use to talk to the drone using an FTP-like protocol.

See: http://forum.developer.parrot.com/t/minidrone-characteristics-uuid/4686/3
See: https://developer.parrot.com/docs/SDK3/ARSDK_Protocols.pdf

The two characteristics for ftp-like transmission (using ARDataTransfer library) are 0xfd23 and 0xfd53

I'd look at other implementations for reference to see how it works exactly.