Create config for frontend or backend seperately

1. init_web_config: create Config object for frontend, load
   configuration from `web_config.py`.
2. init_backend_config: create Config for backend, load configuration
   from `backend_config.py`.

And two new classes inherit from `Config` in config.py:

1. WebConfig: representing the orchestrator frontend web configuration
2. BackendConfig: representing the orchestrator backend workers
                  configuration

Before calling init_{web,backend}_config, check sys.argv, if
"fedmsg-hub*", "celery" or "build_module_locally" is present, it's
running as backend.

tests/__init__.py

@@ -14,7 +14,7 @@ import koji
 import module_build_service
 from module_build_service import db
 from module_build_service.utils import get_rpm_release, import_mmd, mmd_to_str
-from module_build_service.config import init_config
+from module_build_service.config import init_web_config
 from module_build_service.models import (
     ModuleBuild, ModuleArch, ComponentBuild, VirtualStream,
     BUILD_STATES,
@@ -25,7 +25,7 @@ from module_build_service.db_session import db_session
 
 base_dir = os.path.dirname(__file__)
 app = module_build_service.app
-conf = init_config(app)
+conf = init_web_config(app)
 
 
 def staged_data_filename(filename):

tests/test_monitor.py

@@ -8,7 +8,7 @@ import module_build_service.config as mbs_config
 import module_build_service.monitor
 from module_build_service import models
 from module_build_service.db_session import db_session
-from conf.config import TestConfiguration
+from conf.web_config import TestConfiguration
 
 from six.moves import reload_module
 from tests import app, init_data, make_module_in_db