lnwallet: integrate obfuscated state hints into funding workflow

This commit finalizes the implementation of #58 by integrating passing
around the obfuscate state hints into the funding workflow of the
wallet, and also the daemon’s funding manager.

In order to amend the tests, the functions to set and receive the state
hints are now publicly exported.

lnwallet/script_utils_test.go

@@ -547,12 +547,12 @@ func TestCommitTxStateHint(t *testing.T) {
 	for i := 0; i < 10000; i++ {
 		stateNum := uint32(i)
 
-		err := setStateNumHint(commitTx, stateNum, obsfucator)
+		err := SetStateNumHint(commitTx, stateNum, obsfucator)
 		if err != nil {
 			t.Fatalf("unable to set state num %v: %v", i, err)
 		}
 
-		extractedStateNum := getStateNumHint(commitTx, obsfucator)
+		extractedStateNum := GetStateNumHint(commitTx, obsfucator)
 		if extractedStateNum != stateNum {
 			t.Fatalf("state number mismatched, expected %v, got %v",
 				stateNum, extractedStateNum)