downgrade waterways

A lot of streams in OSM are of minor importance, they certainly
should show up lower in the list of results than villages. Those
rivers/streams that are well known have a wikipedia page and get
a higher importance from that.

The disadvantage with downgrading is that the address gets even
more useless but that's something that needs to be solved outside
the rank search.

settings/address-levels.json

@@ -63,7 +63,11 @@
           "sea" : [4, 0]
       },
       "waterway" : {
-          "" : [17, 0]
+          "river" : [19, 0],
+          "stream" : [22, 0],
+          "ditch" : [22, 0],
+          "drain" : [22, 0],
+          "" : [20, 0]
       },
       "highway" : {
           "" : 26,