Submodules: Reverting submodule back to our fork of the Horizontal List View project

It was a GitHub problem which is now fixed.
Merge pull request #564 from arthurbenemann/Submodules

Submodules: Reverting submodule back to our fork of the HorizontalListView
HeartBeat: Extracts the heartbeat code to a new class
HeartBeat: Moving the heartbeat class to inside the drone class.
HeartBeat: Moving  all heartbeat variables to inside the heartbeat class
HeartBeat: Make the heartbeat class store the last ID received from the system.
HeartBeat: Make the heartbeat state change fire a droneEvent.

TTS outputs are now handled via the drone events.
Merge pull request #566 from arthurbenemann/HeartBeat_issue565

Refactoring of the HeartBeat code