make downloads from IPFS gateways optional

I would prefer if downloading from IPFS gateways were opt-in, or if there were at least a way to opt-out.

Right now this only affects the current alpha version of F-Droid client. also see: DownloaderFactory.java#L90@1.16-alpha2

Edited Jan 01, 2023 by Michael Pöhn

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information