Improve the ability to configure Player CSS

* Adds ability to override player CSS.
* Every player now has `.anm-player` class which is only CSS entry point used to style a player.
* Every player instance now has `.anm-player-<canvas-id>` class which is only CSS entry point used to style this concrete player instance.
* The same as above for `Controls` canvas and `InfoBlock` canvas, the classes are `.anm-controls` and `.anm-info` respectively.
* Adds ability to specify ribbons color.
* Detaching player is done properly now, all (or most of) player's custom properties are removed now canvas when player is detached. Seems it improved player performance.
* `findByName` both for `Scene` and `Element`.

Know issues to solve:
* If several players were created on one page, browser stores a CSS class instance for each of them.
* Ribbons, if semi-transparent are seen not to be cleared between frames, I'm investigating in that.
Moving all our canvas vars into `cvs.__anm (= {width, overlays, etc})` would simplify getting rid of it a lot