This commit implements the simplification within the latest version of
BOLT-0007. With this change, we simply sign the message hash directly
with the bitcoin keys, rather than signing the node keys themselves.
This commit implements some minor coding style, commenting and naming
clean up after the recent major discovery service was merged into the
codebase.
Highlights of the naming changes:
* fundingManager.SendToDiscovery -> SendAnnouncement
* discovery.Discovery -> discovery.AuthenticatedGossiper
The rest of the changes consist primary of grammar fixes and proper
column wrapping.
