Cleans up the Android status bar notifications code and handles clicks
on the notification, calling the onclick() callback defined on the
notification in Javascript.
Several things here:
- Add support for the W3C notifications spec, and rewrite the old API to
call the new W3C one behind the scenes.
- Notifications are now automatically cleared when the user clicks.
- Clicking the notification brings the user to the same instance of the
app as was already running (and not a new copy as by default in
Android notifications).
- Support for multiple notifications from one app using tags, as
specified in the W3C spec and supported by Android.
- Support for canceling a single notification by tag, as per W3C spec.
Callbacks to Javascript when the user clicks are specified but not yet
supported; I will add that assuming I can get Android to call some code
in the plugin when the notification is clicked.
