Added option to remove fullscreen- and airplay-button & Added images to assets-folder

[jpunz]

This may be useful and i changed that for one of my projects. Also the images which are used by the player-control buttons should be placed in the assets-folder, which i have changed here - otherwise they are not visible.

[jpunz]

I just added a bugfix (see commit message)

[jpunz]

Additionally fixed a bug