Update logging in channel and channelmanager to better levels

This updates a number of log sites in channel and channelmanager to
 * Be a bit more verbose at the TRACE level,
 * Move some error/useful messages to the ERROR/WARN/INFO level,
 * Add new logs to always log once at the DEBUG level when we
   send/receive a commitment_signed (with some extra data),
 * Include the channel id being operated on in more log messages.

Author: TheBlueMatt