Make v2 job status look more like v1.

Adds a header line to each task in a task status line specifying the
instance number, host, etc., the way v1 did. (We had originally
planned not to display that information in v2, but we also have tests
that depend on it being present.)

Bugs closed: AURORA-874

Reviewed at https://reviews.apache.org/r/26982/
Script to build mesos.native egg in clean vagrant environment

Our integration tests have been broken recently by a lack of available
precompiled mesos.native eggs. This patch adds a script to build them
so that anybody can upgrade our mesos version without breaking our
e2e tests.

Added README to
https://svn.apache.org/repos/asf/incubator/aurora/3rdparty

Testing Done:
eggs in https://svn.apache.org/repos/asf/incubator/aurora/3rdparty
were built with this script.

Reviewed at https://reviews.apache.org/r/26962/