sub menus didn't get checked for being active.

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

Updated to avoid full tree traversal.
Also noticed ```activateItems``` didn't do anything so that's been fixed.
Update CHANGELOG.md
Fixes #2726: ActiveRecord now fills default values on creating new instance of the model if defaults are available from DB schema
Fixes #2805
Merge branch 'nav-active' of github.com:Alex-Code/yii2 into Alex-Code-nav-active

Conflicts:
	extensions/bootstrap/CHANGELOG.md
	extensions/bootstrap/Nav.php
New french messages
better to use strict comparison as much as possible
Merge pull request #2818 from RusAlex/319_strict_comparison_theme

better to use strict comparison as much as possible
Default values init moved to a method that should be called manually
Adjusted unit tests, added description to docs
Merge pull request #2815 from yiisoft/ar-default-values

Fixes #2726: ActiveRecord now fills default values on creating new instance of the model if defaults are available from DB schema
Merge pull request #2819 from drenty/french-messages

New french messages
Fixed typo
Proposal: GII generate strings for I18N
Fixed typo
Fixed getting default value from postgres schema
Fixed getting default values from schema for SQLite
Merge branch 'ar-default-values'
Merge branch 'origin/master'