Add support for Linode driver

• https://github.com/linode/docker-machine-driver-linode

• Make machine and machine options configurable

• Add build step for Linode driver

• Add configuration using Linode's CoreOS (linode/containerlinux) image and one of the new Dedicated CPU instances (g6-dedicated-2)

Deploying this will also require updating the monitor to support both DO and Linode, which is a blocker otherwise manual monitoring is required.