New truncate and truncateWords methods

New truncate and truncateWords methods, https://github.com/yiisoft/yii2/issues/2941
Update BaseStringHelper.php

Length check.
Update CHANGELOG.md
Update BaseStringHelper.php

Updated to use mb_* functions
Test case for new truncate methods.

Test case for new truncate methods.
Update BaseStringHelper.php
Issue #3154 - DataColumn filter model validation error indication added
Issue #3154 - GridView - list of filter model validation errors added to summary
Issue #3154 - DataColumn checkForFilterErrors() now use Html::addCssClass
Update BaseStringHelper.php
Changelog update
BaseListView - errors rendering added
GridView - error rendering scheme changed
GridView/DataColumn - moved error list display into GridView
DataColumn - error detection moved into renderFilterCellContent()
Fixes #1263: Fixed the issue that Gii and Debug modules might be affected by incompatible asset manager configuration
Merge branch 'master' of git://github.com/yiisoft/yii2
Fixes #3216: Fixed the bug that `yii.activeForm.destroy()` did not remove `submit` event handlers
phpdoc issue

[ci skip]
Fixes #3216.