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.
Update QueryBuilder.php

Fixed some errors – syntax with ";" after closure function and also moved building of unions queries into this function.
Update Query.php

Change union method to accept also <code>$all</code> variable. TRUE means that we must results <code>UNION ALL</code> construction, FALSE – that <code>UNION</code>.
Update QueryBuilder.php

Delete some spaces from result string.
Update Query.php

Forget one ";" :D
doc link fixes
fixed stringHelper dirname to return empty string

in case no dir is present
subwidgets should be rendered in the same view
Update Query.php

Change passing parameters to array with two elements – 'all' which means if we use UNION or UNION ALL construction and 'query' which is our sql query that will be at right of construction.
Update QueryBuilder.php

Change buildUnion method to be ready to accept parameters in <code>['all' => $all, 'query' => $query]</code> format for division to "UNION" and "UNION ALL" constructions.
doc link fixes
Update Query.php

Using short array syntax.
Update QueryBuilder.php

Change <code>array_reduce</code> with anonimous function variant to easy string collection from pieces of unions.