To provider better REST API support PATCH method is added which is used
for partial updates, while a PUT should only update whole record.

issues #303 and yiisoft/yii#2664

Password input in advanced app signup [ci skip]

Doc Fixes

* 'master' of github.com:yiisoft/yii2:
  minor doc fix.
  minor doc improvement.
  Add echo into docs for link pager
  Update migration.md. Fix missed quotes
  handle array in importNamespaces.
  import namespaces.
  import namespaces.
  renamed autoload to classmap.
  Added autoload command.
  Rewording
  Added readme and license files to extensions.
  fixed the "only" option for FileHelper::findFiles()
  Added Query::indexBy
  Improved FileHelper::filterPath()
  Enhanced file options for FileHelper.
  Fixed locale command.

replaces #618

Add echo into docs for link pager

I'm not sure if echo should be mentioned, but without the echo before the LinkPager::widget() the user would see nothing.

Update migration.md. Fix missed quotes