Added Nav widget closes #367
Added NavBar widget closes #437
Merge branch 'upstream' into 367-bootstrap-nav

* upstream:
  typo in Html helper
  Created a \yii\web\VerbFilter
  Implemented MaskedInput widget.
  Use class constants for Event declatration in ActionFiler
  Removed unused method.
  Updated requirements about yii\i18n\Formatter
  refactored numberformatting in base\Formatter
  Fixes issue #439
  Fixed typos in new Formatter classes
  Fixes issue #441: InvalidRequestException should be HttpException
  Removed breaking tests.
  Removed breaking test.
  Added "formatter" app component.
  Finished Formatter.
  formatter WIP.
  Added missing use statement.
  Fixed some wording
refactored based on comments (2nd round)
fix namespaces
register asset bundle instead
Merge pull request #438 from tonydspaniard/367-bootstrap-nav

[ready]Added Bootstrap Nav and NavBar widgets 367 bootstrap nav