implement hard mode

seems to work OK.  Could be sped up by local filters instead of
ingesting every tx from the block but I can do that later if
performance (mostly disk i/o) is an issue

once multiple connections are implemented, hard mode should forward
txs to blend in.

shell.go

@@ -51,7 +51,7 @@ func shell() {
 	// setup spvCon
 
 	SCon, err = uspv.OpenSPV(
-		SPVHostAdr, headerFileName, dbFileName, &Store, Params)
+		SPVHostAdr, headerFileName, dbFileName, &Store, true, Params)
 	if err != nil {
 		log.Fatal(err)
 	}