Add support for constrainst annotations

[HamzaBenyazid]

Using annotations from javax.validation.constraints is very common in developing an app using JEE, spring or any other java framework. It's used to validate field values of java beans.
For example :

import javax.validation.constraints.NotNull;
import javax.validation.constraints.Size;

public class User {
    @NotNull
    private String username;

    @Size(min = 6, max = 20)
    private String password;

    // Constructor, methods, etc.
}

A good feature to have is to generate these beans respecting the constraints annotations.
These annotations serve as just metadata, and will not validate until you use a validator, like Hibernate Validator.

So the goal is to implement a way for reading these constraints and generate objects that respect them