Fix loop modes affecting children

I decided to merge it without part of the tests, since this fix is important to everyone. Do created an issue to finish them later for myself.

This one turns back the important two lines in `player.js`, when parent repeat-modes for groups did affected children not in the proper way and introduces part of the tests for them.

Minor additional change: `__preRender` function for `Element`, not to mess with additional conditions for `customRender`, introduced by @alexeypegov.