Add note about order in dist_between query

nlmapsweb/templates/tutorial_chapters/7.html

-<p>With the second type of distance query we can ask for the distance between two named things.</p>
+<p>With the second type of distance query we can ask for the distance between two named things. Please note that the order of the two things matters: What appears first in the NL query should also appear first in the MRL query!</p>
 
 <div class="task">
     <ol>