Ignore command line arguments that are not flags.

Review: https://reviews.apache.org/r/14812
Moved src/mesos to src/cli.

Review: https://reviews.apache.org/r/14813
Added 'mesos::internal::detect' for CLI tools.

Review: https://reviews.apache.org/r/14814
Added an 'HDFS' abstraction.

Review: https://reviews.apache.org/r/14815
Made 'mesos' be a "subcommand dispatcher" and added the 'resolve',
'execute' and 'ps' subcommands.

Review: https://reviews.apache.org/r/14816
Fixed regression in properly gc'ing completed executors.

Review: https://reviews.apache.org/r/14937
Removed unimplemented Dashboard page.

The Dashboard page has been stubbed in the webUI for a while but has not
received any attention yet. It is misleading when a user clicks on the
navigation and doesn't understand what the graphs mean.

The files are not used for anything else, and so they can safely be
removed without affecting the rest of the UI. D3 and Cubism can be
re-added later if they prove useful.

Review: https://reviews.apache.org/r/14657
Fixed GarbageCollectorIntegrationTest.ExitedFramework test.

Review: https://reviews.apache.org/r/14944
Corrected reference to "$routeParams".

It was missing an "a".

Review: http://reviews.apache.org/r/14948
Fixed GroupTest.MultipleGroups test.

Review: https://reviews.apache.org/r/14961
MESOS-511 Update documentation home and remove outdated drafts pages.