Fixes issue #3740 for horizontal layouts

Enh: MongoDB model gii generator

mimeTypes Validator is wrong

I'm find error

```php

Wrong
 } elseif (!empty($this->mimeTypes) && !in_array(FileHelper::getMimeType($file->tempName), $this->mimeTypes, true)) {

Correct
} elseif (!empty($this->mimeTypes) && !in_array(FileHelper::getMimeType($file), $this->mimeTypes, true)) {
```

Not need call '$file->tempName' because getMimeType get object $_FILE => $file, so use $file and validator works fine

Updated pt-BR translation

fixed note about search class

File validator adjusted

Russian guide. Start forms

\yii\i18n\DbMessageSource code style fixes

Excess \yii\base\Model::resolveFields() method removed

Fix .gitignore for `basic` and `advanced` application templates

Fix #3756: Convert values to float for number formatting