Ability to init player from container

This Pull Request should be the first one for version `v1.2` when it will be merged.

From now on, player should be initialized from `<div>` tag or any container tag, but not `<canvas>`. Though, it will not break if `<canvas>` was used for initialization, but will make a warning in console. Change your `<canvas>` to `<div>` and the warning is gone!

Among with it:

* Ability to pass snapshot URL using a parameter of a wrapper (and it will be improved even more in next PR)
* Any private data used by player which was stored before using direct `__anm`-prefixed properties of an element is now stored in a separate `elm.__anm` object to ease removing and also isolate these private properties in one container (and may be move them to player finally in some future) (@mcm69 thx for idea).