platform/filesystem_notifications/monitor/darwin/fsevents_daemon.py imports reactor, installing default instead of qt4reactor

[Mike McCracken]

On windows and darwin, the qt4reactor has to be installed first for ubuntuone-control-panel-qt to work. That code imports platform for credentials, but doesn't need filesystem_notifications.

The issue is that platform/__init__ imports monitor, installing the default reactor, before ubuntuone-control-panel-qt installs the qt4reactor. Since control-panel doesn't need filesystem_notifications, the solution is to remove the 'convenience' import of monitor into platform.