[android] Tweak the online bridge to tell native when an event has happened.

This allows the native side to not send excess events.
[android] Move non-plugin files out of plugins/ subdirectory.
[android] Don't catch exceptions wihtin the bridge since the browser does better logging of them when uncaught.
Revert "[android] Don't catch exceptions wihtin the bridge since the browser does better logging of them when uncaught."

This reverts commit 8937f29ee8aa58568db94865860c86615acf23ca.

I checked it in too hastily. It doesn't actually work as I wanted. Needs
more thinking...
[all] [CB-4725] Export cordova version as "cordova.version"