multi: use witnessScript everywhere instead of redeemScript

This commit consists of a mass variable renaming to call the pkScript being executed for segwit outputs the `witnessScript` instead of `redeemScript`. The latter naming convention is generally considered to be reserved for the context of BIP 16 execution. With segwit to be deployed soon, we should be using the correct terminology uniformly through the codebase. 

In addition some minor typos throughout the codebase has been fixed.

lnwallet/script_utils_test.go

@@ -16,13 +16,13 @@ import (
 // the commitment transaction.
 //
 // The following spending cases are covered by this test:
-//   * Alice's spend from the delayed output on her commitment transaciton.
+//   * Alice's spend from the delayed output on her commitment transaction.
 //   * Bob's spend from Alice's delayed output when she broadcasts a revoked
 //     commitment transaction.
 //   * Bob's spend from his unencumbered output within Alice's commitment
 //     transaction.
 func TestCommitmentSpendValidation(t *testing.T) {
-	// We generate a fake output, and the coresponding txin. This output
+	// We generate a fake output, and the corresponding txin. This output
 	// doesn't need to exist, as we'll only be validating spending from the
 	// transaction that references this.
 	fundingOut := &wire.OutPoint{
@@ -82,7 +82,7 @@ func TestCommitmentSpendValidation(t *testing.T) {
 	}
 	sweepTx.TxIn[0].Sequence = lockTimeToSequence(false, csvTimeout)
 	signDesc := &SignDescriptor{
-		RedeemScript: delayScript,
+		WitnessScript: delayScript,
 		SigHashes:    txscript.NewTxSigHashes(sweepTx),
 		Output: &wire.TxOut{
 			Value: int64(channelBalance),