gstlal_etg + related files: added ability to process channels in parallel (via...

gstlal_etg + related files: added ability to process channels in parallel (via condor) as well as serially, added tracking of jobs by job_id (parallel) and subset_id (serial) to reflect this. Added a few options in Makefile, gstlal_etg_pipe to tune level of serial/parallel processing