Javadoc for OverlayNG package.

Signed-off-by: Martin Davis <[email protected]>

modules/core/src/main/java/org/locationtech/jts/operation/overlayng/package.html

@@ -82,6 +82,12 @@ <h2>Semantics</h2>
   have valid <code>MultiPolygon</code> topology.)</li>
 <li>Empty results are atomic <code>EMPTY</code> geometries 
   of dimension appropriate to the operation.</li>
+<li>As far as possible, results preserve the order and direction of the inputs.
+  For instance, a MultiLineString intersection with a Polygon
+  will have resultants which are in the same order and have the same direction
+  as the input lines (assuming the input lines are disjoint).
+  If an input line is split into two or more parts, 
+  they are ordered in the direction of occurence along their parent line.</li>
 </ul>
 
 </p>