Added `yii\web\Request::get($name = null, $defaultValue = null)` and `yii\web\Request::post($name = null, $defaultValue = null)`

fixes #2093

issue #2093

issue #2043

added a fallback for handling all request types

fixes #2066, related to #2043

Fixes #2063: Removed `yii\web\Request::acceptTypes` and renamed `yii\web\Request::acceptedContentTypes` to `acceptableContentTypes`.
Renamed `yii\web\Request::acceptedLanguages` to `acceptableLanguages`

Fixed URL parsing so it's now properly giving 404 for URLs like `http://example.com//////site/about`

and 7ba6a063

when $_SERVER['HTTPS'] is "ON" it doesn't work well

- added example code for application components
- added missing short description

[ci skip]