This commit introduces a ChannelParty type to LND. It is useful for
consolidating all references to the duality between the local and
remote nodes. This is currently handled by having named struct rows
or named boolean parameters, named either "local" or "remote". This
change alleviates the programmer from having to decide which node
should be bound to `true` or `false`. In an upcoming commit we will
change callsites to use this.
This commit adds new hash and preimage types. These types are
similar to chainhash.Hash, except for that string representations
are not reversed.
The reason for adding dedicated types and not use [32]byte, is to
facilitate logging (%v displays as hex string) and have
standard methods to convert from byte slice and string with a
length check.
