vagrant: fix a typo/bug in swift config
vagrant: set up `demo` user credentials

This makes it easier to use swift/zerocloud as either `admin` or `demo`.
vagrant: separate admin and demorc files

For testing zapps with multiple users, it's useful to have separate
environmental config files.
Merge pull request #140 from larsbutler/vagrant-minor-tweaks

Vagrant: minor tweaks