Support for Openbenchmarking.org test suites

Rally should include support for openbenchmarking.org and phoronix-test-suite tests and test suites. Openbenchmarking.org and Phoronix test suite have a large number of advanced tests that the Openstack community should be able to leverage via Rally as the official Openstack benchmarking utility.

This could be in the form of Rally python libraries that translate PTS test suites into something Rally understands, or also in the form of extending Rally to import and run them natively.