Added preview of the current playback speed and video quality in the VideoOptionsFragment

[Poslovitch]

This PR introduces a "preview" of the current video playback speed and quality, as follows: (the previews are underlined in red)

I'm publishing this PR as a draft, because I need your technical help and opinions about two things:

1. Playback speed is currently displaying the speed float. I am planning to make use of the strings (e.g. 1.25x instead of 1.25, Normal instead of 1.0). However, I'm afraid the code will be clumsy. Any tips for this?
2. See the comments I made down below.

[sschueller]

For the speed I am not sure what the most elegant solution would be. You could try using two array to do the translation float to string resource: https://stackoverflow.com/a/21614742/1152320 . or maybe cast the float to a string and tag it to the end of the key of a string resource;: https://stackoverflow.com/questions/43722367/android-dynamic-key-names-r-string

[Poslovitch]

Alright thanks, I'll go with the latter.

maybe cast the float to a string and tag it to the end of the key of a string resource;: https://stackoverflow.com/questions/43722367/android-dynamic-key-names-r-string

[Poslovitch]

Done!

[sschueller]

Thanks

[sschueller]

There are a few bugs: https://github.com/sschueller/peertube-android/issues/207