[BetterPhpDocParser] Add support for parsing Doctrine annotations

[TomasVotruba]

1) Rector\DoctrinePhpDocParser\Ast\PhpDoc\EntityTagValueNode

<?php

use Doctrine\ORM\Mapping as ORM;

/**
 * @ORM\Entity(readOnly=true, repositoryClass="Rector\DoctrinePhpDocParser\Tests\PhpDocParser\OrmTagParser\Class_\Source\ExistingRepositoryClass")
 */
final class SomeEntity
{

}

2) Rector\DoctrinePhpDocParser\Ast\PhpDoc\ColumnTagValueNode

<?php

use Doctrine\ORM\Mapping as ORM;

final class FromOfficialDocs
{
    /**
     * @ORM\Column(type="integer", name="login_count", nullable=false, options={"unsigned":true, "default":0}, columnDefinition="CHAR(2) NOT NULL")
     */
    private $loginCount;
}