Automatically create top level folders during init if they don't exist

[Makeshift]

If you create a new team drive and try to stick it into the pool then rclone will fail to create the union because the top level encrypted folder doesn't exist.

There probably isn't a reason why we shouldn't just create that folder for the user so the union works and they don't need to manually make a folder. Might cause duplication issues?

[Makeshift]

Honestly, could PR the union mount to not care and just simply ignore it, but that might annoy some people :)