Removing `abstract` in Module

Update Migration.php

add ability to use an array in multi columns parameters

Merge branch 'fixtures_except_option_added' of https://github.com/Ragazzo/yii2 into Ragazzo-fixtures_except_option_added

* 'fixtures_except_option_added' of https://github.com/Ragazzo/yii2:
  filter fix
  changelog added
  changes of other pr reverted
  except option added

Conflicts:
	framework/CHANGELOG.md

Corrected an error in the inline validator doc

Make HelpController check to make sure module controller path exists

French : minor fixes

fixes #1875

Fix typo version

https://github.com/yiisoft/yii2/blob/master/extensions/redis/Cache.php#L16

fix #1992: when set yii\captcha\CaptchaValidator::$captchaAction = '/sit...

BaseHtml::listBox() incorrect array_key_exists() usage fix

Html::activeDropDownList() and 'multiple' option fix

BaseHtml::listBox() default size settings removed

yii\captcha\CaptchaValidator->createCaptchaAction() error

Fixes #2003: Added `filter` property to `ExistValidator` and `UniqueValidator` to support adding additional filtering conditions

Fixes #1998 : get input value from hidden field when necessary

Using VarDumper::dumpAsString() instead var_export() in the Request pane...

Some Basic App readme updates [skip ci]