[SPARK-6284] [MESOS] Add mesos role, principal and secret

Mesos supports framework authentication and role to be set per framework, which the role is used to identify the framework's role which impacts the sharing weight of resource allocation and optional authentication information to allow the framework to be connected to the master.

Author: Timothy Chen <tnachen@gmail.com>

Closes #4960 from tnachen/mesos_fw_auth and squashes the following commits:

0f9f03e [Timothy Chen] Fix review comments.
8f9488a [Timothy Chen] Fix rebase
f7fc2a9 [Timothy Chen] Add mesos role, auth and secret.