Use protection module without video element

Created by: bbert

This PR enables using protection controller in order to deal with licenses without attaching a video element to the player.

This can be useful to obtain a license without playing a stream. As to anticipate persistent license support in chrome, an example use case is to retrieve and store licensein CDM when recording a stream in order to enable playback afterwards while being disconnected from network.

A sample is provided to demonstrate license acquisition using ProtectionController.

Additionnaly, we could eventually add an API in MediaPlayer or ProtectionController to get a license as it is done in the sample.