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/btcwallet/btcwallet.go

@@ -57,7 +57,7 @@ type BtcWallet struct {
 var _ lnwallet.WalletController = (*BtcWallet)(nil)
 
 // New returns a new fully initialized instance of BtcWallet given a valid
-// confirguration struct.
+// configuration struct.
 func New(cfg *Config) (*BtcWallet, error) {
 	// Ensure the wallet exists or create it when the create flag is set.
 	netDir := networkDir(cfg.DataDir, cfg.NetParams)

lnwallet/btcwallet/signer.go

@@ -96,7 +96,7 @@ func (b *BtcWallet) fetchPrivKey(pub *btcec.PublicKey) (*btcec.PrivateKey, error
 //
 // This is a part of the WalletController interface.
 func (b *BtcWallet) SignOutputRaw(tx *wire.MsgTx, signDesc *lnwallet.SignDescriptor) ([]byte, error) {
-	redeemScript := signDesc.RedeemScript
+	witnessScript := signDesc.WitnessScript
 
 	privKey, err := b.fetchPrivKey(signDesc.PubKey)
 	if err != nil {
@@ -105,7 +105,7 @@ func (b *BtcWallet) SignOutputRaw(tx *wire.MsgTx, signDesc *lnwallet.SignDescrip
 
 	amt := signDesc.Output.Value
 	sig, err := txscript.RawTxInWitnessSignature(tx, signDesc.SigHashes, 0,
-		amt, redeemScript, txscript.SigHashAll, privKey)
+		amt, witnessScript, txscript.SigHashAll, privKey)
 	if err != nil {
 		return nil, err
 	}