Fixes #1222: removed Slider widget from JUI extension since it's not input widget and a wrapper doesn't really add anything

Changed usage of self to static to allow extendibility

fixes #1244

fixes #1246

code style section has been added here:
https://github.com/yiisoft/yii2/wiki/Core-framework-code-style#self-vs-static

verification code for properties:
https://gist.github.com/cebe/7566916

issue #1246

also made everything conistent with client validation

this allows to be able to call error action.

fixes #1244

fixes #1220

Small edit for consistency with frontend config.

Small edit for consistency with /apps/advanced/backend/config/main.php. Sorry, my OCD kicked in.

Update script filter

```map``` and ```indexOf``` on arrays were only added in IE9.
Changed to make use of jQuery's equivalents.

fixes #1230

Duplicate

Duplicate APC requirement removed

issue #1228