core: Add the MachineReadable UI, --machine-readable flag
commands/status: add machine-readable output
website: document machine-readable output
commands/box: list has machine-readable output
website/docs: ask for input
Merge branch 'f-machine-readable'

This adds the foundation for supporting machine-readable output. This
purposely doesn't add much machine-readable output, because we want to
learn from the community what people want.

This also isn't a full API for controlling Vagrant. Rather, it is a way
to programmatically script Vagrant commands.
Update CHANGELOG