MXS-1300: Make output optional

Minor refactoring to the core library to allow multiple calls from within
the same program.

Added --quiet option to silence output so that tests aren't so
verbose. Currently this only works on UNIX based systems.

maxctrl/lib/start.js

@@ -28,6 +28,6 @@ exports.builder = function(yargs) {
         .usage('Usage: start <command>')
         .help()
         .command('*', 'the default command', {}, () => {
-            console.log('Unknown command. See output of `help start` for a list of commands.')
+            logger.log('Unknown command. See output of `help start` for a list of commands.')
         })
 }