Cert: Use setuptools to provision GD cert tests

* Create setup.py that implements setup() from setuptools to
  provision GD cert tests in an enviornment
* Change makefile configuration such that both GD tests and the
  latest ACTS framework is packed in the same file. This helps
  prevent version mismatch between GD cert tests and ACTS framework
* Output a single bluetooth_cert_tests.zip that include above packages
  instead of two separate ZIP archives
* Running "gd/setup.py install" will install both GD tests and ACTS
  framework and it is recommended to do this in virtual environment
* Package target binaries into generic directory name "target/" so that
  GD cert tests do no need to know the name of the product being tested
* Find GD root directory via its relative with cert library directory
  so that we do not rely on os.getcwd()
* Added two more flags to gd/cert/run to allow custom test config,
  and the ability to re-use existing virtualenv
* Generate python file must be in a files sub-directory to avoid
  packing the resultant zip archive in itself

Test: source gd/cert/run --host
Bug: 150321998
Change-Id: I34b05b0ad121c8df35207f437a0326b52a4645e2