[Uk] Guide corrections [skip ci]

fix  mistake small  [skip ci]

Fixes #6514: advanced application SignupForm::signup() should not return User model if saving failed

Fixes #6467: `ActiveForm` will scroll to the nearest visible element when the first error input is hidden

Removed User.role from advanced application template because it was causing confusion that user could be assinged a single RBAC role and that role field is somehow tied to RBAC at all.

better readability

require PHP mcrypt extension

eg. used in /var/www/app/vendor/yiisoft/yii2/base/Security.php at line 465

AssetBundle can not be imported because the class already exists in this namespace.

fixes #6475

fixed hhvm build.

[skip ci] Add new translation messages and translate that for fa-IR language.

Spanish docs Theming [skip ci]

Signed-off-by: nabi <nabikaz@gmail.com>

docs/guide/input-forms.md - small fix [ci skip]

/docs/guide-ja/input-forms.md added [ci skip]

Yii2 basic code coverage added

Update from original

Fixes #6404: advanced application template `Alert` widget was generating duplicate IDs in case of multiple flashes

/docs/guide-ja/db-migrations.md added [ci skip]