Render maritime admin boundaries less prominently

This requires rendering admin boundaries based on the individual
lines, rather than the entire polygons.

* This fixes #621
* This possibly impacts solutions to #723, #2234m and #2663.

admin.mss

@@ -1,4 +1,5 @@
 @admin-boundaries: #ac46ac;
+@admin-boundaries-maritime: darken(@water-color,15%);
 
 /* For performance reasons, the admin border layers are split into three groups
 for low, middle and high zoom levels.
@@ -16,6 +17,9 @@ overlapping borders correctly.
       background/line-width: 1.2;
       line-join: bevel;
       line-color: @admin-boundaries;
+      [maritime = 'yes'] {
+        line-color: @admin-boundaries-maritime;
+      }
       line-width: 1.2;
     }
     [zoom >= 5] {
@@ -43,6 +47,9 @@ overlapping borders correctly.
       background/line-width: 0.6;
       line-join: bevel;
       line-color: @admin-boundaries;
+      [maritime = 'yes'] {
+        line-color: @admin-boundaries-maritime;
+      }
       line-width: 0.6;
     }
     [zoom >= 7] {
@@ -63,6 +70,9 @@ overlapping borders correctly.
       background/line-color: white;
       background/line-width: 0.4;
       line-color: @admin-boundaries;
+      [maritime = 'yes'] {
+        line-color: @admin-boundaries-maritime;
+      }
       line-join: bevel;
       line-width: 0.4;
       line-clip: false;
@@ -116,6 +126,9 @@ overlapping borders correctly.
     background/line-width: 2;
     line-join: bevel;
     line-color: @admin-boundaries;
+    [maritime = 'yes'] {
+      line-color: @admin-boundaries-maritime;
+    }
     line-width: 2;
     line-dasharray: 6,3,2,3,2,3;
     line-clip: false;
@@ -126,6 +139,9 @@ overlapping borders correctly.
     background/line-width: 2;
     line-join: bevel;
     line-color: @admin-boundaries;
+    [maritime = 'yes'] {
+      line-color: @admin-boundaries-maritime;
+    }
     line-width: 2;
     line-dasharray: 6,3,2,3;
     line-clip: false;
@@ -138,6 +154,9 @@ overlapping borders correctly.
       background/line-width: 1.5;
       line-join: bevel;
       line-color: @admin-boundaries;
+      [maritime = 'yes'] {
+        line-color: @admin-boundaries-maritime;
+      }
       line-width: 1.5;
       line-dasharray: 5,2;
       line-clip: false;
@@ -156,6 +175,9 @@ overlapping borders correctly.
       background/line-width: 2;
       line-join: bevel;
       line-color: @admin-boundaries;
+      [maritime = 'yes'] {
+        line-color: @admin-boundaries-maritime;
+      }
       line-width: 2;
       line-dasharray: 2,3;
       line-clip: false;

project.mml

@@ -1093,11 +1093,12 @@ Layer:
       table: |-
         (SELECT
             way,
-            admin_level
+            admin_level,
+            tags->'maritime' as maritime
           FROM planet_osm_roads
           WHERE boundary = 'administrative'
             AND admin_level IN ('0', '1', '2', '3', '4')
-            AND osm_id < 0
+            AND osm_id > 0
           ORDER BY admin_level DESC
         ) AS admin_low_zoom
     properties:
@@ -1111,11 +1112,12 @@ Layer:
       table: |-
         (SELECT
             way,
-            admin_level
+            admin_level,
+            boundary
           FROM planet_osm_roads
           WHERE boundary = 'administrative'
             AND admin_level IN ('0', '1', '2', '3', '4', '5', '6', '7', '8')
-            AND osm_id < 0
+            AND osm_id > 0
           ORDER BY admin_level DESC
         ) AS admin_mid_zoom
     properties:
@@ -1129,11 +1131,12 @@ Layer:
       table: |-
         (SELECT
             way,
-            admin_level
+            admin_level,
+            boundary
           FROM planet_osm_roads
           WHERE boundary = 'administrative'
             AND admin_level IN ('0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '10')
-            AND osm_id < 0
+            AND osm_id > 0
           ORDER BY admin_level::integer DESC -- With 10 as a valid value, we need to do a numeric ordering, not a text ordering
         ) AS admin_high_zoom
     properties: