Implement automatic refresh of the DC/OS token

[sjahreis]

See this workaround to accomplish automatic refresh of the DC/OS token: https://medium.com/@richardgirges/authenticating-open-source-dc-os-with-third-party-services-125fa33a5add#.qyiniam1a

Afterwards no user interaction should be necessary.

[sjahreis]

See this page to select a lib: https://jwt.io/