Add rendering for bicycle_parking

* Add bicycle_parking icon from z18 or (for areas) 750 pixels, whichever is
  earlier.
* Add yellow background for bicycle_parking (like regular parking).

Thanks to @nebulon42 for the icon.

This resolves gravitystorm#591 and part of gravitystorm#108.

amenity-points.mss

@@ -229,6 +229,16 @@
     }
   }
 
+  [feature = 'amenity_bicycle_parking'] {
+    [zoom >= 18],
+    [way_pixels > 750] {
+      marker-file: url('symbols/bicycle_parking.18.svg');
+      marker-placement: interior;
+      marker-clip: false;
+      marker-fill: @transportation-icon;
+    }
+  }
+
   [feature = 'amenity_pharmacy'][zoom >= 17] {
     marker-file: url('symbols/pharmacy.16.svg');
     marker-fill: @health-color;

landcover.mss

@@ -467,6 +467,16 @@
     [way_pixels >= 64] { polygon-gamma: 0.3;  }
   }
 
+  [feature = 'amenity_bicycle_parking'][zoom >= 13] {
+    polygon-fill: @parking;
+    [zoom >= 15] {
+      line-width: 0.3;
+      line-color: saturate(darken(@parking, 40%), 20%);
+    }
+    [way_pixels >= 4]  { polygon-gamma: 0.75; }
+    [way_pixels >= 64] { polygon-gamma: 0.3;  }
+  }
+
   [feature = 'aeroway_apron'][zoom >= 10] {
     polygon-fill: @apron;
     [way_pixels >= 4]  { polygon-gamma: 0.75; }