Adding 'validating' and 'validated' events
Hooking before/after methods for create, update, validate and delete to model events

- removal of blank before/afterSave methods, as having blank methods for all hooks would clutter the class
* closures passed as arguments to save/forceSave now get hooked as another function to saving/saved events [BREAKING]
* forceSave() now calls save(), that have an additional $force argument [DRY]
+ minor improvements on methods documentation