CBQE:0 runsystest.py - automation script for system tests

Added --testcfg param to identify testcfg file from tests/testcfg directory and overwrite pysystests/testcfg.py and import params from it

Change-Id: I734e0bf7dc416de0c371e1d335439e604294e365
Reviewed-on: http://review.couchbase.org/36550
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Tommie McAfee <tommie@couchbase.com>
Tested-by: Aruna Piravi <aruna@couchbase.com>