allow setInitialMediaSettingsFor with fragmentedText media type

[jeffcunat]

This PR will make setInitialMediaSettingsFor compatible with fragmentedText (like it is done with audio and video)

For example :

 player.setInitialMediaSettingsFor('fragmentedText', { 
                lang: 'en',
                role: 'caption'
            });

This is useful to initialize the player for users that want to activate closed captions by default if they are present.

We are using the mediaController.matchSettings method inside the TextController to reuse the same mechanism than for audio and video.

We can keep the setTextDefaultLanguage method for backward compatibility but
player.setInitialMediaSettingsFor('fragmentedText', { lang: 'en' }); is equivalent to player.setTextDefaultLanguage('en')

[jeffcunat]

@dsilhavy Note that today, dash.js player enables text by default if any.
We could also make a PR to disable text by default. Does it make sense ?

Moreover, localStorage is actually used to store audio and video media settings.
I have noticed that dashjs_fragmentedText_settings is also stored but never used anywhere.
We could allow to use it to set the same text language than the previous stream (or of the same stream if we reload). Would be another PR ?

[dsilhavy]

@jeffcunat Thanks for this PR, I added some minor comments. In addition:

• Can you please add a warning to the setTextDefaultLanguage and getTextDefaultLanguage function that they are deprecated and will be removed in version 3.2.0. Might also be good to refer to the two functions which replace the aforementioned.
• I agree that text tracks should be disabled by default. Can you please change the enabled parameter to false.
• Would be nice to have the default text settings in the local storage as well. If you can implement that I would prefer a new PR for that.

[jeffcunat]

I will provide another PR soon for keeping text settings in local storage.

[dsilhavy]

Perfect, thanks