fixes Bug 1090376 - new setup.py entry point for the setupdb_app

eliminate a bit of code and make a new entry point for the setupdb_app in setup.py

plus a couple clean up things:
* rename the SetupDB class to SetupDBApp to make the class work with the upcoming automatic app discovery mechanism
* drop the default stderr logging level for SetupDBApp to ERROR from CRITICAL
* 
should be ```socorro```