ADD METHOD: \yii\db\Schema::createColumnSchema()

Now i am creating MySQL application what will work with UUID's, so i need to override `ColumnSchema::{db,php}Typecast` to convert it between string and binary. But in `\yii\db\mysql\Schema::loadColumnSchema` it's [hardcoded](https://github.com/yiisoft/yii2/blob/master/framework/db/mysql/Schema.php#L130), and no way to override w/o overriding and copypasting long method !

P.S.. Also see #1221