[Feature Request] Possibility to run from webdav

[Cees2439867]

If database is stored on webdav it is possible to use multiple devices on the same database.

[TheLastProject]

This seems similar to #20. I think if we have an auto backup (#23) together with conflict solving support (#512), auto import (no issue) and propagation of deletion on import (no issue) this would be easy to do in a sync service agnostic way (in your case, just set up your WebDav client to sync that file).

I think I will create new issues for the last steps later, so everything is in place to make this possible.

I want to not directly sync the database as this would cause a lot of additional complexity and using the import export code we can stick to one known code path

[TheLastProject]

Closed in favor of #791.