Analytics labels and media composition updates during playback

This releases makes it possible to update analytics labels and media composition during playback. Previously, this information could only be provided when starting playback.

Simply set the analyticsLabels (if you are using SRGAnalytics_SRGMediaPlayer.framework) or mediaComposition (if you are using SRGAnalytics_SRGDataProvider.framework) properties with the updated values when appropriate.