Structs for Wire Protocol HTLCs and Commitments

* Structs and wire messages for HTLCs
* Wire protocol for a state machine with no blocking(!!!)
  (I will write the state machine)
  TL;DR: Can do multiple HTLC modifications in-flight, dead simple wire
  protocol. Both sides can update their Commitments unliaterally without
  waiting for the other party's signature. Will have basic/preliminary
  notes in the README
* Added **swp to .gitignore because of vim annoyances

lnwire/commit_revocation.go

@@ -0,0 +1,82 @@
+package lnwire
+
+import (
+	"fmt"
+	"io"
+)
+
+//Multiple Clearing Requests are possible by putting this inside an array of
+//clearing requests
+type CommitRevocation struct {
+	//We can use a different data type for this if necessary...
+	ChannelID uint64
+
+	//Height of the commitment
+	//You should have the most recent commitment height stored locally
+	//This should be validated!
+	//This is used for shachain.
+	//Each party increments their own CommitmentHeight, they can differ for
+	//each part of the Commitment.
+	CommitmentHeight uint64
+
+	//Revocation to use
+	RevocationProof [20]byte
+}
+
+func (c *CommitRevocation) Decode(r io.Reader, pver uint32) error {
+	//ChannelID(8)
+	//CommitmentHeight(8)
+	//RevocationProof(20)
+	err := readElements(r,
+		&c.ChannelID,
+		&c.CommitmentHeight,
+		&c.RevocationProof,
+	)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+//Creates a new CommitRevocation
+func NewCommitRevocation() *CommitRevocation {
+	return &CommitRevocation{}
+}
+
+//Serializes the item from the CommitRevocation struct
+//Writes the data to w
+func (c *CommitRevocation) Encode(w io.Writer, pver uint32) error {
+	err := writeElements(w,
+		c.ChannelID,
+		c.CommitmentHeight,
+		c.RevocationProof,
+	)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (c *CommitRevocation) Command() uint32 {
+	return CmdCommitRevocation
+}
+
+func (c *CommitRevocation) MaxPayloadLength(uint32) uint32 {
+	return 36
+}
+
+//Makes sure the struct data is valid (e.g. no negatives or invalid pkscripts)
+func (c *CommitRevocation) Validate() error {
+	//We're good!
+	return nil
+}
+
+func (c *CommitRevocation) String() string {
+	return fmt.Sprintf("\n--- Begin CommitRevocation ---\n") +
+		fmt.Sprintf("ChannelID:\t\t%d\n", c.ChannelID) +
+		fmt.Sprintf("CommitmentHeight:\t%d\n", c.CommitmentHeight) +
+		fmt.Sprintf("RevocationProof:\t%x\n", c.RevocationProof) +
+		fmt.Sprintf("--- End CommitRevocation ---\n")
+}