Modest refactoring

1. Updated method signatures on ConfigurationSettingsType
Consequence:
+ More readable code for our use cases
+ Signature is different than what's required by the __metaclass__ attribute

The latter is OK because we do not require and will not support __metaclass__ attribute usage
2. Added constant configuration `ReportingCommand.ConfigurationSettings.streaming=False
3. Improved error message in SearchCommand.py

Signed-off-by: David Noble <dnoble@splunk.com>