csrf docs added

Fixes #1681: Added support for automatically adjusting the "for" attribute of label generated by `ActiveField::label()`

mail component in basic app

Merge branch 'debug_module_improvements' of github.com:Ragazzo/yii2 into Ragazzo-debug_module_improvements

Conflicts:
	extensions/yii/debug/panels/DbPanel.php

Updated git-workflow.md to remove a false link

Refactored tests.

Replaced link to gitref.org to try.github.com as gitref.org is down.

enhance Inflector  helper with ascii function

* upstream:
  Fixed CSRF token masking issue.
  improved error message of calling invalid scope method.
  Fixed repo URL
  Fixes #1650: Added Connection::pdoClass.
  code style fix.
  added changelog
  codestyle fix
  improved checkIntegrity method
  Modified extension guidlines
  fix sphinx command signature
  fixed bug with forgotten param, fixed behavior for one table integrity
  fixed sequence reset
  added postgresql features to reset seq/check integrity

added postgresql features to reset seq/check integrity

fixed sequence reset

Modified extension guidlines

* upstream: (21 commits)
  Fixes #1643: Added default value for `Captcha::options`
  Fixes #1654: Fixed the issue that a new message source object is generated for every new message being translated
  Allow dash char in ActionColumn’s button names.
  Added SecurityTest.
  fixed functional test when enablePrettyUrl is false.
  fixed composer.json
  minor doc fix.
  Fixes #1634: Use masked CSRF tokens to prevent BREACH exploits
  Use better random CSRF token.
  GII unique indexes avoid autoIncrement columns
  updated debug retry params.
  Added sleep().
  Added unit test for ActiveRecord::updateAttributes().
  Fixes #1641: Added `BaseActiveRecord::updateAttributes()`
  Fixed #1504: Debug toolbar isn't loaded successfully in some environments when xdebug is enabled
  Mongo README.md updated.
  Fixes #1611: Added `BaseActiveRecord::markAttributeDirty()`
  Number validator was missing
  Fixes #1638: prevent table names from being enclosed within curly brackets twice.
  Unique indexes rules for single columns into array
  ...