+ remove unused mutating methods

+ cleanup&style

include/mapnik/grid/grid.hpp

@@ -79,7 +79,7 @@ public:
 
     hit_grid(int width, int height, std::string const& key, unsigned int resolution);
 
-    hit_grid(const hit_grid<T>& rhs);
+    hit_grid(hit_grid<T> const& rhs);
 
     ~hit_grid() {}
 
@@ -110,31 +110,16 @@ public:
         return names_;
     }
 
-    inline std::set<std::string> property_names()
-    {
-        return names_;
-    }
-
     inline feature_type const& get_grid_features() const
     {
         return features_;
     }
 
-    inline feature_type& get_grid_features()
-    {
-        return features_;
-    }
-
     inline feature_key_type const& get_feature_keys() const
     {
         return f_keys_;
     }
 
-    inline feature_key_type& get_feature_keys()
-    {
-        return f_keys_;
-    }
-
     inline std::string const& get_key() const
     {
         return key_;

src/grid/grid.cpp

@@ -48,7 +48,7 @@ hit_grid<T>::hit_grid(int width, int height, std::string const& key, unsigned in
       }
 
 template <typename T>
-hit_grid<T>::hit_grid(const hit_grid<T>& rhs)
+hit_grid<T>::hit_grid(hit_grid<T> const& rhs)
     : width_(rhs.width_),
       height_(rhs.height_),
       key_(rhs.key_),