Implement schema reading via schema providers

[lotyp]

There is draft implementation currently in cycle-bridge:

https://github.com/spiral/cycle-bridge/pull/91

There is also documentation about implementation, that was made in Yii framework:

https://github.com/yiisoft/yii-cycle/blob/master/docs/guide/en/reading-schema.md https://github.com/yiisoft/yii-cycle/blob/master/docs/guide/ru/reading-schema.md