Add new guide upload-file

1.  UploadedFile::getInstances($model, 'file'); sees only one file if not set ```'file[]'```

```php
<?= $form->field($model, 'file[]')->fileInput(['multiple' => '']) ?>
```

2. ```$form->errorSummary(..)``` not return all errors of file attribute, but only the last.
So I had to invent.

```php
if ($model->hasErrors()) {
    echo '<pre>';
    print_r($model->getErrors());
    echo '</pre>';
}
```

So it should be?
MS SQL Server fix for older versions than 2012 (alternative solution)

This alternative solution LIMIT, OFFSET problem SQL Server version older than 2012.
fix error

fix error when if fields whose names are reserved word
Update QueryBuilder.php

fix error occurs when you use multiple databases.
Update QueryBuilder.php

solution used **heukirne** for the names of columns.
Gii codestyle fixes
Fixed tests
Gii codestyle fixes #2
Merge pull request #3739 from umneeq/gii-codestyle-fixes-2

Fix Gii template variables order
Fixed typo
Merge pull request #2975 from githubjeka/patch-1

Add new guide upload-file
Renamed file upload docs
start-hello page in Russian
Merge branch 'master' of git://github.com/yiisoft/yii2 into guide-start-hello
Fixed formatting, added note about work in progress
small fixes
Adjusted file upload guide wording
Merge pull request #3742 from MUTOgen/guide-start-hello

Russian Guide. Start-hello
Adjusted Russian guide on writing hello world app
Edited

Looks good!