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.
fix #3478

it correct work with integer keys of list
Update QueryBuilder.php

solution used **heukirne** for the names of columns.
Added ability to generate dropdown from Enum field

Alternatively, if statement could be: if(substr($column->dbType, 0, 4) === 'enum'), however expected implemented option to be more robust across other database formats.

Created after followup on this issue:  https://github.com/yiisoft/yii/issues/292#issuecomment-44780779
Fix #3196: Masked input widget revamped to use new plugin
Fix #3196: Masked input widget revamped to use new plugin

Edited Asset Bundle PHP doc header information.
Merge pull request #3688 from yiiframework-com-ua/master

Unnecessary line (left after yiisoft@b39effd) [skip ci]
Formatting changes to new enum field
diagram update [skip ci]
Merge pull request #1 from yiisoft/master

pull
Set expire to null so CookieCollection::has work
line to changelog
fix align
fix issue number
Merge pull request #3692 from SonicGD/fix-cookies

Fixed the issue that `CookieCollection::has` always returns false for cookies from browser
improved gii input filter, fixes #3689
Merge pull request #3676 from enigmatix/master

Added ability to generate dropdown from Enum field