Update Dockerfile to use the new syntax

This changes the Dockerfile to use "setup" rather than "--setup" which changed recently. Also makes the mp binary wait so that Docker doesn't terminate after starting up.

Lastly, we change the directory structure to the new linux location

You can run this by doing this:

sudo docker run -i -d -v /mnt/mailpile-data/:/.local/share/Mailpile -v /mnt/mailpile-encryption:/.gnupg -p 33411:33411 -t Mailpile