* creocoder-incorrect-checking-sqlite-version:
  improved db test, avoid error by accessing db directlry
  fixed failure on sqlite version check
  Correct SQLite version checking

always use getConnection()

ensure PDO instance has been created at this point

fixes #6741

always use unique directory for each test

only the phpManager configuration was described, the DbManager configuration was not found on this documentation

close #6771

http://en.wikipedia.org/wiki/Year_2038_problem

formatting date and time values for years >=2038 or <=1901 is now possible also with intl extension is
installed. 32bit systems will fall back to the PHP implementation because intl uses a 32bit UNIX timestamp internally.
On a 64bit system the intl formatter is used in all cases if installed.

fixes #5577

[skip ci] Fix Arabic File Type Validation Message

Added content to give a clear example to those that don't intuitively know how to set the template property using array notation.

close #6811

[skip ci] Update intro-upgrade-from-v1.md

fixes #6748

[skip ci] Fix typo in spanish translation

- ensure HTML version is acutally HTML formatted
- added valid text version

fixes #6814
original issue #6748

docs/guide/tutorial-performance-tuning.md better wordings[ci skip]

docs/guide-ja/tutorial-performance-tuning.md - added [ci skip]

* 'master' of github.com:yiisoft/yii2:
  Update test-fixtures.md
  docs/guide-ja/tutorial-mailing.md - added [ci skip]
  docs/guide/tutorial-mailing.md - corrections [ci skip]
  docs/guide/tutorial-i18n.md revised [ci skip]
  Fixed typo
  docs/guide-ja updated [ci skip]
  docs/guide-ja/tutorial-i18n.md - completed [ci skip]
  docs/guide-ja/tutorial-i18n.md - WIP
  docs/guide-ja/tutorial-i18n.md - WIP [ci skip]
  docs/guide-ja/tutorial-i18n.md - WIP [ci skip]
  Update start-hello.md
  yii\db\ActiveQuery phpDoc fix

docs/guide-ja/tutorial-mailing.md - added [ci skip]

docs/guide/tutorial-mailing.md - corrections [ci skip]