Implement TaskLauncher for Metronome

[trisberg]

Metronome seems to be the new framework for scheduling short running jobs on Mesos, taking over from Chronos. See https://github.com/dcos/metronome

[cppwfs]

While testing Task Partitioning on SCDF-Mesos, several Chronos issues popped up.

• Chronos attaches command-line-arguments to the mesos id. Thus you can't include : or / so users can't use command line args to configure jdbc properties for example. Else it will throw a ZK exception
• Once a task fails, Chronos would queue up other tasks but would not execute them.
• Unable to reproduce: but on 2 occurrences tasks were left in staged but did not execute.

So this story is required for SCDF-Mesos task framework.