Nested rule - combine dot notation and nested structure

[arogachev]

Moved from yiisoft/validator#200.

Initially reported by @a6colute.

[vjik]

 'body.shipping' => [
      Required::rule(),
      Nested::rule([
          'phone' => [MatchRegularExpression::rule('/^\+\d{11}$/')],
      ]),
],

It's not correct rules format. Dot notation don't support in rules. It's allow in Nested only and o far only for public properties.

Correct rules:

'body' => new Nested([
	'shipping' => [
		new Required(),
		new Nested([
		  'phone' => new Regex('/^\+\d{11}$/'),
		]),
	]
]),

See test here: #10