New hooks, exceptions and relationsData array

• addition of before/afterSave, Update, Delete and Validate hooks, that are called by the model when the given events happen, with no arguments (changed from the RC)
• addition of Ardent::throwOnFind boolean property to forcefully throw exceptions when models are not found (forcing usage of findOrFail)
• addition of InvalidModelException, enabled by Ardent::throwOnValidate
• addition of Ardent::relationsData static attribute that makes it much easier to define relations, cleaning the clutter in models with many relationships
• cleaner code, following code style rules (almost PSR-2, except for braces)