feat: Improve the ORM

[pythonbrad]

Problem

The ORM don't permit to do some operations (will be describe below) directly in the database.
It's will be useful and better to be able to do it. Solve this problem, will also permit to replace the usage of special attributes who was a short-term solution.

Example

Count a set of objects

Before

count($question->answers);

Expected

$question->answers->count();

Verify if a set of objects exists

Before

if (count($question->answers)) {
   ...
}

Expected

if ($question->answers->exists()) {
  ...  
}

Delete a set of objects

Before

foreach ($question->answers as $answer) {
    $answer->delete();
}

Expected

$question->answers->delete();

Order a set of objects

Before

function score($quiz)
{
    return $quiz->score;
}
array_filter($user->quizzes, "score")

Expected

$user->quizzes->orderBy("score");