Improved music page. New buttons, translations.

Improved music page:
 - New buttons for 'listen' and 'buy'.
 - Added English translations to tv projects.

    application/models/music_model.php
    application/views/pages/music.php
    css/music.css
    images/icons/buy-white-20.png   (+)
    images/icons/listen-black-20.png   (+)
    images/icons/listen-white-20.png   (+)