Updating features archetype to talk about user-facing features.

This includes both giving advice about what should/shouldn't be
considered user-facing feautures as well as suggestions for -rest and
-ui features that provide RESTCONF and DLUX functionality to the base
user-facing feature.

Change-Id: I7a37c74adad8443cc50984b172c74e97cec13c84
Signed-off-by: Colin Dixon <colin@colindixon.com>
Merge "Updating features archetype to talk about user-facing features."