Default to a higher column width.

This avoids the log jumping widths every time the server starts, which
is jarring while debugging.  This value is long enough to fit the UUIDs
in BOSH session IDs.

core/loggingmanager.lua

@@ -199,7 +199,7 @@ function log_sink_types.nowhere()
 end
 
 -- Column width for "source" (used by stdout and console)
-local sourcewidth = 20;
+local sourcewidth = 45;
 
 function log_sink_types.stdout(config)
 	local timestamps = config.timestamps;