Now the app can:
-Set the channel name and description
-Set the notification subtext
-Add a "Close" action to the notification, along with customizing the action text and icon

Fixed bugs:
-Icon is never used if it's in "drawable" rather than "mipmap"
-Used "Compat" library to make backwards compatibility easier

…kground-mode

Android notifications have a "how long ago was this notification set" timer.

Now there's an option to turn that off (the default is true, so it's shown, matching current behavior).

I got the error message that "onactivate" does not exist with the latest HEAD Version. I therefore investigated and found out that since the on() function has been changed, I think this has been forgotten to also be changed in the Java file.

…ground-mode

If you had two apps using this plugin running, clicking "Close" on a notification for one would close both.

Apply fix from katzer#419 (comment)

Remove Windows platcform from plugin.xml to allow install on cordova >9