Rename condor_ce_generator to condor_ce_config_generator

Name should provide a hint as to what it's generating. I considered
naming it condor_ce_collector_config_generator but that's probably
overkill.
Use subprocess instead of exec to run condor_ce_reconfig

This allows us to report success or failure within the condor_ce_config_generator program.
Revise text in auto-generated config file to be more clear

Also, made sure the comment text is consistent between the pre-packaged
config file and the generated config file.