Implement ActiveForm and ActiveField

Conflicts:
	extensions/bootstrap/CHANGELOG.md
	extensions/bootstrap/Nav.php

Updated to avoid full tree traversal.
Also noticed ```activateItems``` didn't do anything so that's been fixed.

* 'feature' of https://github.com/mongosoft/yii2:
  returned back formatting language files
  code style. WHILE
  code style. FOR
  code style. FOREACH
  code style. operator IF
  @param, @var, @property and @return must declare types as boolean, integer, string, array or null
  short echo tags
  short array syntax

Conflicts:
	extensions/apidoc/commands/RenderController.php
	extensions/apidoc/models/BaseDoc.php
	extensions/apidoc/models/Context.php
	extensions/apidoc/templates/bootstrap/Renderer.php
	extensions/apidoc/templates/bootstrap/layouts/guide.php
	extensions/apidoc/templates/bootstrap/layouts/main.php
	extensions/apidoc/templates/bootstrap/views/index.php
	extensions/apidoc/templates/html/Renderer.php
	extensions/apidoc/templates/offline/views/index.php
	extensions/apidoc/templates/offline/views/offline.php
	extensions/apidoc/templates/online/views/index.php
	extensions/elasticsearch/Connection.php
	extensions/redis/ActiveQuery.php
	framework/base/ErrorException.php
	framework/helpers/BaseFileHelper.php
	tests/unit/framework/helpers/FileHelperTest.php

Based off the method in ```Menu.php``` I've updated ```Nav``` so it will check if sub menus are active or not.

replaced keyword "yii" with "yii2" in composer.json files (fixes #2557)

fixes #2466

Fixes #1881: Improved `yii\bootstrap\NavBar` with `containerOptions`, `innerContainerOptions` and `renderInnerContainer`

Merge branch 'request-params-refactoring' of github.com:cebe/yii2 into cebe-request-params-refactoring

Conflicts:
	framework/CHANGELOG.md