Fixes for issues with unsubscription and skipping of poll notifications 

One issue is serious: typo (missed reference sign &) resulted in context property was unsubscribed forever - no notifications about changes in the monitored file. Also disabling QSocketNotifier while processing activation resulted in skipped poll notifications, so clients sometimes are unaware on property changes.

Also 2 tools was added: contextkit-monitor to monitor contextkit properties changes in provided namespace and filemon to check how poll notification monitoring is working with statefs.

Also there are some less influencing improvements and clean-ups.