Remove separate cluster/telematics demo features

Now that the layer reorganization from SPEC-3723 has landed, the cluster and telematics demo features are for the most part redundant, as they are empty.  Since at present there is no obvious immediate need to keep them, I propose removing them and ensuring that they build correctly in a tree configured with just the "agl-demo" feature.  Ideally, all of the demo platform images including html5 would be buildable in one tree in this fashion.