Make minimum landuse zoom levels more consistent

The minimum zoom levels are currently rather inconsistent. For example meadow
and farmland have a different minimum zoom level. This PR aims to improve this.

This PR lets all major landuse start at z10 (like most do already), except for
wood / forest. Smaller objects will start at z13.

Concrete changes in minimum zoom levels:

* tourism=camp_site, tourism=caravan_site, tourism_picnic_site from z13 to z10
* landuse=quarry from z11 to z10
* landuse=garages from z12 to z13
* landuse=farmyard, landuse=farm, landuse=farmland from z9 to 10
* landuse=village_green from z11 to z10
* natural=desert from z8 to z10 (solves partially gravitystorm#773)
* aeroway=apron, aeroway=aerodrome from z12 to z10
* highway=services, highway=rest_area from z14 to z10

landcover.mss

@@ -70,7 +70,7 @@
   [feature = 'tourism_camp_site'],
   [feature = 'tourism_caravan_site'],
   [feature = 'tourism_picnic_site'] {
-    [zoom >= 13] {
+    [zoom >= 10] {
       polygon-fill: @campsite;
       polygon-opacity: 0.5;
       line-color: saturate(darken(@campsite, 60%), 30%);
@@ -82,7 +82,7 @@
     polygon-fill: @attraction;
   }
 
-  [feature = 'landuse_quarry'][zoom >= 11] {
+  [feature = 'landuse_quarry'][zoom >= 10] {
     polygon-pattern-file: url('symbols/quarry2.png');
     line-width: 0.5;
     line-color: grey;
@@ -125,7 +125,7 @@
     }
   }
 
-  [feature = 'landuse_garages'][zoom >= 12] {
+  [feature = 'landuse_garages'][zoom >= 13] {
     polygon-fill: @garages;
     polygon-opacity: 0.2;
   }
@@ -205,7 +205,7 @@
     }
   }
 
-  [feature = 'landuse_farmyard'][zoom >= 9] {
+  [feature = 'landuse_farmyard'][zoom >= 10] {
     polygon-fill: @farmyard;
       [zoom >= 16] {
         line-width: 0.5;
@@ -218,7 +218,7 @@
 
   [feature = 'landuse_farm'],
   [feature = 'landuse_farmland'] {
-    [zoom >= 9] {
+    [zoom >= 10] {
       polygon-fill: @farmland;
       [zoom >= 16] {
         line-width: .5;
@@ -234,7 +234,7 @@
     }
   }
 
-  [feature = 'landuse_village_green'][zoom >= 11] {
+  [feature = 'landuse_village_green'][zoom >= 10] {
     polygon-fill: @grass;
   }
 
@@ -306,7 +306,7 @@
     }
   }
 
-  [feature = 'natural_desert'][zoom >= 8] {
+  [feature = 'natural_desert'][zoom >= 10] {
     polygon-fill: @desert;
   }
 
@@ -353,11 +353,11 @@
     }
   }
 
-  [feature = 'aeroway_apron'][zoom >= 12] {
+  [feature = 'aeroway_apron'][zoom >= 10] {
     polygon-fill: @apron;
   }
 
-  [feature = 'aeroway_aerodrome'][zoom >= 12] {
+  [feature = 'aeroway_aerodrome'][zoom >= 10] {
     polygon-fill: @aerodrome;
     polygon-opacity: 0.2;
     line-width: 0.2;
@@ -370,7 +370,7 @@
 
   [feature = 'highway_services'],
   [feature = 'highway_rest_area'] {
-    [zoom >= 14] {
+    [zoom >= 10] {
       polygon-fill: @rest_area;
     }
   }