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
Merge pull request #2714 from drenty/master

Added asElapsedTime function to Formatter
Made Theme::basePath optional fixes #2810
reverted deletion of Theme::getPath()
fixed Theme::getPath()
Merge pull request #2811 from dmeroff/theme_enhancements

Made Theme::basePath optional fixes #2810
throw exception when UrlManager is not properly configured in console mode.
Updated Spanish translation
Typo fix
Update yii.php
Merge pull request #2814 from djfly/patch-3

Update yii.php
Removed app translation file
Merge pull request #2813 from lucianobaraglia/master

Updated spanish translation
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