added missing view property to PageCache

fixes #544
static instead of self for creating instances

in UploadedFile::loadFilesRecursive
fixes #542
Renamed view to getView().
draft idea of action based responses
doc clarification.
Renamed some folders to fit changed app structure.
implementation of Response tied to actions

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
Changed existing code to match the changes regarding response
Merge pull request #547 from suralc/advanced-rename

Renamed some folders to fit changed app structure.
Merge pull request #548 from cebe/action-response

implementation of Response tied to actions
Revert "Merge pull request #548 from cebe/action-response"

This reverts commit 9d7597d61a51ae7030b667f740c2a97471cf7f6e, reversing
changes made to 6b6390f72b6a6010cfbe614aab236a90d10b1a00.