tools: notifier: more changes in NotificationProperties

split validate into sub calls (validateBasic, validateEmail ...) to sections.
as more sections are expected in following commits (validateFilter, validateSnmp ).
Order methods (constructor befor any other method).
Apply code style & add requireAll and requireOne methods.

Change-Id: I2ebbf76a23c79d354cb9026dc3ad0f4310a804be
Signed-off-by: Mooli Tayer <mtayer@redhat.com>