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
Added asElapsedTime function
Typo in asElapsedTime description
Call Yii::t everytime instead of passing a template variable
Typo
asElapsedTime can now take DateInterval as parameter
asElapsedTime style improvements
asElapsedTime can now take a DateInterval string as a parameter
fixes #2739
Merge pull request #2742 from tonydspaniard/2739-rest-createaction-bug

fixes #2739
doc fix [skip ci]
fix sql query
Merge pull request #2746 from AlexGx/doc-small-fix

fix sql query
Added support for inverted intervals (future time) and unit tests
Removed debug code, changed doc
doc fix [skip ci]
Fixes #2303: support setting basePath and baseUrl as aliases during runtime.
Fixes #735: Added back `ActiveField::hiddenInput()`