Add option for GM report to dump to a file

This patch adds the option to Guru Meditation report to dump report to a
file instead of stderr. If passed a log_dir parameter when calling
setup_autorun() method, the report will be dumped to a file named
<SERVICE_NAME>_gurumeditation_<TIMESTAMP> in the specified log_dir.

This patch also adds service_name parameter to the setup_autorun() which
will be defaulted to the top python module filename if omitted..

Change-Id: If5a7e9731b81c76506613e2617c33613d295937a