+reflect background_image in python and add background_color to match XML

CHANGELOG.md

@@ -43,6 +43,8 @@ TODO - fill these out more:
 - geometry closed
 - feature api better - context's provide schema support
 
+- Python: exposed Map `background_image` (and aliased `background` to `background_color`)
+
 - Python: exposed BuildingSymbolizer
 
 - Support in the CSV plugin for reading JSON encoded geometries (#1392)

bindings/python/mapnik_map.cpp

@@ -370,12 +370,30 @@ void export_map()
         .add_property("background",make_function
                       (&Map::background,return_value_policy<copy_const_reference>()),
                       &Map::set_background,
-                      "The background color of the map.\n"
+                      "The background color of the map (same as background_color property).\n"
                       "\n"
                       "Usage:\n"
                       ">>> m.background = Color('steelblue')\n"
             )
 
+        .add_property("background_color",make_function
+                      (&Map::background,return_value_policy<copy_const_reference>()),
+                      &Map::set_background,
+                      "The background color of the map.\n"
+                      "\n"
+                      "Usage:\n"
+                      ">>> m.background_color = Color('steelblue')\n"
+            )
+
+        .add_property("background_image",make_function
+                      (&Map::background_image,return_value_policy<copy_const_reference>()),
+                      &Map::set_background_image,
+                      "The optional background image of the map.\n"
+                      "\n"
+                      "Usage:\n"
+                      ">>> m.background_image = '/path/to/image.png'\n"
+            )
+
         .add_property("base",
                       make_function(&Map::base_path,return_value_policy<copy_const_reference>()),
                       &Map::set_base_path,