Architecture improvements

[piotrpasich]

This PR shows a bunch of improvements:

• Removed functions.php (the function inside was used only in one class, so there is no reason to keep it there)
• Created an ability to change the behavior of the builder.
• Created new behavior of builder which allows user to use own factory methods to create objects (ex. when they want to trigger events during adding objects).
• Protected state of Definition class (it's impossible to change Definition now - DDD way)
• Refactored factories finder class
• Refactored classes' dependencies to allow users to change the save methods to use other ORMs inthe future (ex. not Eloquent, but Doctrine).
• Automated tests fixed for current phpunit implementation