Add module controller namespace in config

fixes #5218

related to #5083

fix typo

Added a note that pluralization of controller IDs in RESTful endpoints by yii\rest\UrlRule doesn't always simply add "s" to the end of the controller ID.  I cited an example of controllers whose IDs end in the letter "x", for example "BoxController", whose RESTful endpoints are pluralized to "boxes"

related to #5128

with help of ##English on freenode :)

fixes #5244

just fixed typo

In line 180. 
It should be .val() instead of .value.

This is my first edit.

Add comment to documentation sample code for GridView

fixes #2593