Omi connection notification should be non-dismissible persistent notification

Right now on android, if you swipe away the 'omi connected' notification, it dismisses and then it will randomly disconnect your Omi. If you open the app, the notification does not reappear and you need to force close the app and reopen it for the notification to come back. Please upgrade the notification and the service so it does not close in the background and maintain better connectivity to your omi