Fixes for iOS 11

• fixes for iOS 11.
• fixes for duplicate event add.
• fixes draggable view on exit PIP modality.

Fix PIP modality releasing

• fix strong to weak for containerView and mainParent

Fixes PIP mode

• fixes player releasing on PIP mode
• fixes visibility notification with multiple instance of the player
• added activity indicator

Visibility Notifications

• fix timer visibility for iOS previous 10

Visibility Notification

• fix visibility notification

Visibility Notification

• visibility notification

Picture-in-Picture

• support for PIP

AirPlay

• support for AirPlay.

Subtitles

• support for subtitles .srt

Fix full screen mode on iOS 8

• fix full screen mode on iOS 8