Split exportRemotes out from syncDataRemotes; the parts of the assistant
that upload keys and drop keys from remotes don't apply to exports,
because those operations are not supported.
Some parts of the assistant and webapp do operate on both
syncDataRemotes and exportRemotes. Particularly when downloading from
either of them. Added a downloadRemotes that combines both.
With this, the assistant should download from exports, but it won't yet
upload changes to them.
This commit was sponsored by Fernando Jimenez on Patreon.
46d19648ee