[Reviewer: Rob, From: Alex] Make homestead logging less verbose by default.

This changes crest logging so that:
-  The default log level is INFO. 
-  Some logs have been upgraded to INFO level so they show up by default. 
-  There is a new configuration option to turn the log level down to DEBUG if required.

Feedback by the end of Tuesday please. Let me know if that's going to be a problem.