Add option to display AirPlay artwork and playback info in full screen mode

Fixes #11648
Make some strings translatable so they can be passed on to user
Display notification when opening the audio device failed
Add MythErrorNotification class
Use new MythErrorNotification
Add method to retrieve last error from opening DVD device
Add method to detect if RingBuffer construction actually failed
Add convenience methods to display notifications
Show error should DVD playback not be possible
Show MediaMonitor's errors via notification centre
Update Mac OS eject to use diskutil (disktool is deprecated and removed in 10.9)
Use ShowNotificationError API.

Simplify the code
If creating the RingBuffer encountered an error, display that error.

Playback could fail silently, with the user wondering what happened.
Make BD player reports errors so we can exit early.
Exit early if no title has been found
Make DVD player reports errors so we can exit early
Report file playback (local and remote) report errors
Make http playback reports errors
Make Visibility and Priority field a uint32_t so they can be used as bitmask
Implement Visibility feature in notification. Change how position on screen is calculated: so after a full screen, position restart at 0.

Currently, only kPlayback visibility is implemented....
Fix crashes when playing BD disk with no valid key installed
Redefine visibility and priority bitmask type
Add ability to define priority and visibility with ShowNotificationX(..)