Add support for CAN driven speeds for the demo dashboard

Changes include:
- Update cluster-dashboard recipe to pull in libqtappfw for
  signal-composer support
- Add signal-composer and required low-can and gps bindings to
  agl-cluster-demo-platform image
- Add recipe to install configuration file that tells the
  cluster-dashboard app to use signal-composer vehicle and engine
  speed events instead of running the default animation loop,
  and a new agl-cluster-demo-preload feature template that drives
  adding the recipe to the image for demo purposes.

Bug-AGL: SPEC-3045

Change-Id: I193f9fd764b7610eaacc4c524522552bcc1e7ccc
Signed-off-by: Scott Murray <scott.murray@konsulko.com>