fixes #1055
revert back the change about message class so that the class can be lazily loaded.
Merge pull request #1054 from lucianobaraglia/master

GII - more short echo syntax
Fixes #1056: removed 5.3 compatibiltiy code from ArrayHelper::multisort, fixed phpdoc
Removed check for PHP 5.4 from Session::open()
Removed fallback from mb_parse_str to parse_str from Request::getRestParams since mb_ availability is Yii2 requirement
Reverted 5.4 enhancements on requirements checked to be able to run it on lower PHP versions
'ViewContext' interface extracted, files render workflow refactored to use this interface.
'ViewContext' renamed to 'ViewContextInterface'.
Fixes autoreplacement
Fixes issue #858: Tabs::widget type problem
Merge pull request #1061 from nukkumatti/master

Fixes issue #858: Tabs::widget type problem
Fixes issue #1063: Fatal Error while getting value from ActiveRelation generated by Gii
Fixes #1063
Merge pull request #1068 from nukkumatti/master

Fixes issue #1063: Fatal Error while getting value from ActiveRelation g...
fixes #1066: Added ActiveForm::validate() and validateMultiple()
add sorting icons to gridview sort links in basic and advanced app css
minor code refacotring.
Fixes #1075: changed the default value of GridView::empty.
Fixes issue #1078: Typo in comment