ENH: add option to enable zero-y intercept

app/otbHarmonizer.cxx

@@ -445,8 +445,10 @@ private:
       if (band>0)
         exp << ";";
       exp << "im1b" << (band+1) << "*" << b1;
-      if (b0 != 0)
+      if (b0>0)
         exp << "+" << b0;
+      else
+        exp << "" << b0;
 
       gain[band] = b1;
       offset[band] = b0;