Fixes #1610: `Html::activeCheckboxList()` and `Html::activeRadioList()` will submit an empty string if no checkbox/radio is selected

extended from codeception testcase, added docs

Gii should keep horizontal layout

Bootstrap's dropdown encodes also trailing caret tag

doc fix

Fixed sequence id match for postgresql

PgAdmin generates   sequence as  '"Schema"."Table_seq"'::regclass  when
non public schema is used.

Fixes #1499: Added `ActionColumn::controller` property to support customizing the controller for handling GridView actions

Added support for tagName and encodeLabel parameters in ButtonDropdown

changed install to create-project, added hint

Small correction in DB\Query comments

I checked this using XDebug, and the function actually returns null (which is something different than false). I assume it is the comment that should be changed, and not the code itself...

Renamed `attributeName` and `className` to `targetAttribute` and `targetClass` for `UniqueValidator` and `ExistValidator`.
Refactored UniqueValidator and ExistValidator.

Fixes #1597: Added `enableAutoLogin` to basic and advanced application templates so "remember me" now works properly

Update ActiveField.php

doc fixes