added tabs
add fixes
Refactoring
jQuery UI tabs rework
jQuery UI tabs full rework
Refactoring
Merge branch 'upstream' into 365-bootstrap-tabs

* upstream: (122 commits)
  Refactored StringHelper.
  Line number tweak for error page
  added note about dependency to registerJsFile
  docs: Be explicitly clear about ActiveRecord::create()
  fixed AutoTimestamp example in advanced app
  \yii\rbac\DbManager::isAssigned() signature fix
  Changed the way to set timestamp for multiple attributes.
  Fixes issue #428 Allowing UniqueValidator to be used with non-AR models.
  Better exception page look.
  Removed unnecessary code from MSSQL schema.
  Hover and error line increased by 1 px.
  Error line number fix.
  Error line number fix.
  Error line number fix.
  Lift off!11 #418
  MSIE fix.
  Fixes (theoretically) #418 and #413.
  Removed echo
  RBAC DbManager fixes
  Always refetch the migration table definition.
  ...
Added dropdown widget
Tabs refactored
Added Nav widget closes #367
Added NavBar widget closes #437
Enhance Dropdown to use items as  strings. Remove string=divider rule
Comment for content
Added initial unit testing files for the pgsql driver.
Lost array_merge()
Implemented MaskedInput widget.
Merge branch 'master' of github.com:yiisoft/yii2
Created a \yii\web\VerbFilter

It allows to filter actions by HTTP request methods
typo in Html helper
Refactored based on comments and feedback (3rd round)