* upstream: (2012 commits)
  doc fix.
  Changed the signature of `urlCreator` and button creators for `yii\gridview\ActionColumn`
  parameter adjustment.
  The signature for `yii\gridview\ActionColumn::urlCreator` is changed - the `$action` parameter is moved to the first
  Fixed the signature of Schema::findUniqueIndexes().
  reverted #1598 and added a test for it
  Fix wrong array index in unique indexes for MySql
  Making accesors public
  Get DB unique indexes information
  Fixes #1610: `Html::activeCheckboxList()` and `Html::activeRadioList()` will submit an empty string if no checkbox/radio is selected
  Gii should keep horizontal layout
  Documentation at "yii\authclient" updated.
  Doc comments at "yii\authclient" updated.
  Auth clients "Choice" doc comments updated.
  Auth clients "Choice" widget javascript advanced.
  Bootstrap's dropdown encodes also trailing caret tag
  Auth clients "Choice" widget markup updated.
  Gii should keep horizontal layout
  extended from codeception testcase, added docs
  Auth clients for Facebook, GitHub, LinkedIn added.
  ...

Conflicts:
	framework/yii/helpers/BaseInflector.php
	tests/unit/framework/helpers/InflectorTest.php