Fixes issue #934. Command is created for the selected database, not the default database.

fixes #33

This reverts commit 9d7597d6, reversing
changes made to 6b6390f7.

Result of a discussion with @qiangxue
- there is not global Yii::$app->response anymore, every action has
  dedicated response class
- implementation allows using HMVC pattern now, nested actions do not
  interfer

Name make more sense imo as it is not clear what it handles otherwise.
Removed unused method processRequest form console app and also refactored
console Application to be more similar to web Application.