[Notification] Fix GetULongFromJSONValue

Now GetULongFromJSONValue returns bool and the called decides
what to do when a non-number is passed, and may set the result to
a default number if wanted.

In this case we're setting led_on_period and led_off_period to 0,
because it's the default value.
[Notification] Add support for number and add GetLongFromJSONValue
[Notification] Add support for detail info and is_string() function
Merge pull request #233 from ricardotk/wip-notification

[Notification] Add number and detail info