Added ability to get incoming headers
added basic greek translation
added Greek (el) as available language
removed unnecessary greek translations from core
fixed weird `#` in greek translation
added use http_get_request_headers and use getHeaders method in Gii module
Merge pull request #1958 from 6pblcb/yiiActiveForm-beforeSubmit

Transfer beforeSubmit function after global validation all fields forms
Fixes #1958: `beforeSubmit` in `yii.activeform` is now executed after validation and before form submission
Merge pull request #2111 from dizews/get-headers

Added ability to get incoming headers
Adjustment the translation into Portuguese of Brazil.
Fixes #1974.
Added `beforeRun()` and `afterRun()` to `yii\base\Action`
Fixes #2079:

- i18n now falls back to `en` from `en-US` if message translation isn't found
- View now falls back to `en` from `en-US` if file not found
- Default `sourceLanguage` and `language` are now `en`
Adds docblock comments and HTTP spec links for the new HTTP Exception classes (#2103)
Merge branch 'master' of git://github.com/yiisoft/yii2 into 2103-rename-accessdeniedhttpexception
Removes Map file uploaded accidentally
Condenses changelog notes to 1 line (#2103)
Removed temp class
changelog fix.
Update QueryBuilder.php

Change using of implode to convert array of queries to union to array_reduce. Result of this changing is that code feel difference between two selects that connects with UNION and two selects that connects with UNION ALL.