chainreg: export ChainCode to new pkg

Moves chainCode from the lnd package to the chainreg package,
where it is exported and can be used by other packages.

chainreg/chaincode.go

@@ -0,0 +1,25 @@
+package chainreg
+
+// ChainCode is an enum-like structure for keeping track of the chains
+// currently supported within lnd.
+type ChainCode uint32
+
+const (
+	// BitcoinChain is Bitcoin's chain.
+	BitcoinChain ChainCode = iota
+
+	// LitecoinChain is Litecoin's chain.
+	LitecoinChain
+)
+
+// String returns a string representation of the target ChainCode.
+func (c ChainCode) String() string {
+	switch c {
+	case BitcoinChain:
+		return "bitcoin"
+	case LitecoinChain:
+		return "litecoin"
+	default:
+		return "kekcoin"
+	}
+}