Clean up z13 and z14

* Drop buildings from z13 and z14
* Drop footways from z13
* Drop service roads from z13
* Drop pedestrian roads from z13
* Different rendering of living_street on z13
* Drop playground outlines from z13 and z14
* Lighten up the color of trams
* Drop streams, ditches and drains from z13

buildings.mss

@@ -9,16 +9,12 @@
 @entrance-normal: @building-line;
 
 #buildings {
-  [zoom >= 13] {
-    polygon-fill: @building-low-zoom;
+  [zoom >= 15] {
+    polygon-fill: @building-fill;
     polygon-clip: false;
-    line-width: 0;
-    [zoom >= 15] {
-      polygon-fill: @building-fill;
-      line-color: @building-line;
-      line-width: .75;
-      line-clip: false;
-    }
+    line-color: @building-line;
+    line-width: .75;
+    line-clip: false;
     [amenity = 'place_of_worship'],
     [aeroway = 'terminal'],
     [aerialway = 'station'],

landcover.mss

@@ -106,8 +106,10 @@
   [feature = 'leisure_playground'][zoom >= 13],
   [feature = 'leisure_fitness_station'][zoom >= 13] {
     polygon-fill: @leisure;
-    line-color: darken(@leisure, 60%);
-    line-width: 0.3;
+    [zoom >= 15] {
+      line-color: darken(@leisure, 60%);
+      line-width: 0.3;
+    }
     [way_pixels >= 4]  { polygon-gamma: 0.75; }
     [way_pixels >= 64] { polygon-gamma: 0.3;  }
   }

water.mss

@@ -87,7 +87,7 @@
   [waterway = 'ditch'],
   [waterway = 'drain'] {
     [int_tunnel = 'no'] {
-      [zoom >= 13] {
+      [zoom >= 14] {
         line-width: 2.5;
         line-color: white;
         [waterway = 'stream'][zoom >= 15] {