This commit does to things: moves the prior ShortChannelID struct into
a new short_channel_id.go file, and also implements the new ChannelID’s
currently used within he specification.
These new ID’s are 32-bytes in length and used during initial channel
funding as well as during normal channel updates. During initial
channel funding, the ID is to be a random 32-byte string, while once
normal channel operation has began, the ID is to be (txid XOR index),
where index is the index of the funding outpoint.
Change the name of fields of messages which are belong to the discovery
subsystem in a such way so they were the same with the names that are
defined in the specification.
This commit separates out the ChannelID into a new file, with
additional helper methods for conversion and formatting. With this
commit, the struct is now more general purpose and can be used in the
new routing package, database, and other related sub-systems.
