Major Description
sometimes it is useful for validators to get access to component's model. for example
a) validators can use the model to get value as it was before editing started - ie a password validator that forces the user to change their password
b) validators can access some metadata about the model - ie a model that implements IPropertyReflectionAwareModel
in 1.4 this is done by adding a IModelAwareValidatable#getModel() mixin and casting IValidatable down to it. in 1.5 #getModel() has been introduced direction to IValidatable