Enable ordered_class_elements rule

[paulbalandan]

Description
Enables the rule to be consistent in ordering the class's properties and methods.

$ vendor/bin/php-cs-fixer describe ordered_class_elements
Description of ordered_class_elements rule.
Orders the elements of classes/interfaces/traits.

Fixer is configurable using following options:
* order (a subset of ['use_trait', 'public', 'protected', 'private', 'constant', 'constant_public', 'constant_protected', 'constant_private', 'property', 'property_static', 'property_public', 'property_protected', 'property_private', 'property_public_readonly', 'property_protected_readonly', 'property_private_readonly', 'property_public_static', 'property_protected_static', 'property_private_static', 'method', 'method_abstract', 'method_static', 'method_public', 'method_protected', 'method_private', 'method_public_abstract', 'method_protected_abstract', 'method_public_abstract_static', 'method_protected_abstract_static', 'method_public_static', 'method_protected_static', 'method_private_static', 'construct', 'destruct', 'magic', 'phpunit']): list of strings defining order of elements; defaults to ['use_trait', 'constant_public', 'constant_protected', 'constant_private', 'property_public', 'property_protected', 'property_private', 'construct', 'destruct', 'magic', 'phpunit', 'method_public', 'method_protected', 'method_private']
* sort_algorithm ('alpha', 'none'): how multiple occurrences of same type statements should be sorted; defaults to 'none'

Fixing examples:
 * Example #1. Fixing with the default configuration.
   ---------- begin diff ----------
   --- Original
   +++ New
   @@ -1,30 +1,30 @@
    <?php
    final class Example
    {
        use BarTrait;
        use BazTrait;
        const C1 = 1;
        const C2 = 2;
   -    protected static $protStatProp;
        public static $pubStatProp1;
        public $pubProp1;
   +    var $pubProp2;
   +    public static $pubStatProp2;
   +    public $pubProp3;
   +    protected static $protStatProp;
        protected $protProp;
   -    var $pubProp2;
        private static $privStatProp;
        private $privProp;
   -    public static $pubStatProp2;
   -    public $pubProp3;
        protected function __construct() {}
   -    private static function privStatFunc() {}
   +    public function __destruct() {}
   +    public function __toString() {}
        public function pubFunc1() {}
   -    public function __toString() {}
   -    protected function protFunc() {}
        function pubFunc2() {}
        public static function pubStatFunc1() {}
        public function pubFunc3() {}
        static function pubStatFunc2() {}
   -    private function privFunc() {}
        public static function pubStatFunc3() {}
   +    protected function protFunc() {}
        protected static function protStatFunc() {}
   -    public function __destruct() {}
   +    private static function privStatFunc() {}
   +    private function privFunc() {}
    }

   ----------- end diff -----------

 * Example #2. Fixing with configuration: ['order' => ['method_private', 'method_public']].
   ---------- begin diff ----------
   --- Original
   +++ New
   @@ -1,6 +1,6 @@
    <?php
    class Example
    {
   +    private function B(){}
        public function A(){}
   -    private function B(){}
    }

   ----------- end diff -----------

 * Example #3. Fixing with configuration: ['order' => ['method_public'], 'sort_algorithm' => 'alpha'].
   ---------- begin diff ----------
   --- Original
   +++ New
   @@ -1,8 +1,8 @@
    <?php
    class Example
    {
   -    public function D(){}
   +    public function A(){}
        public function B(){}
   -    public function A(){}
        public function C(){}
   +    public function D(){}
    }

   ----------- end diff -----------

As a possible future enhancement, we can streamline this to sort also the elements by their visibilities (i.e. public, protected, private).

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide