Added support for property validation inheritance

Hey there,

as the title suggests, I've now added support for configurations like this:

config = {
    validations: {
        'BaseType': {
            name: {
                'aa-valid-icon': ''
            }
        },
        'PersonType': {
            name: {
                'aa-inherit': 'BaseType.name',
                required: true
            }
        },
        'UserType': {
            name: {
                'aa-inherit': 'PersonType.name',
                'ng-minlength': '1'
            },
            lastname: {
                'aa-inherit': 'name',
                'ng-minlength': '2'
            }
        }
    }
}

Unit tests are in place as well.