[Notification] Add picojson_helpers.cc

Split picojson_helpers.h into .cc
[Notification] Add GetStringFromJSONValue
[Notification] Add comparison with old image

This will avoid setting the same image
[Notification] Fix progress_value type

progressValue is unsigned long
[Notification] Add support for led and add GetULongFromJSONValue
[Notification] Add support for sound
[Notification] Add support for vibration
Merge pull request #228 from ricardotk/wip-notification

[Notification] Add support for led, sound and vibration