[MeL] Overload Properties::size() for item types.

Counts number of properties on a given mesh item type.

MeshLib/Properties.cpp

@@ -167,4 +167,12 @@ std::map<std::string, PropertyVectorBase*>::size_type Properties::size() const
 {
     return _properties.size();
 }
+
+std::map<std::string, PropertyVectorBase*>::size_type Properties::size(
+    MeshItemType const mesh_item_type) const
+{
+    return count_if(begin(), end(), [&](auto const p) {
+        return p.second->getMeshItemType() == mesh_item_type;
+    });
+}
 }  // end namespace MeshLib

MeshLib/Properties.h

@@ -155,6 +155,9 @@ public:
     std::map<std::string, PropertyVectorBase*>::iterator begin();
     std::map<std::string, PropertyVectorBase*>::iterator end();
     std::map<std::string, PropertyVectorBase*>::size_type size() const;
+    // Counts properties of given mesh item type.
+    std::map<std::string, PropertyVectorBase*>::size_type size(
+        MeshItemType const mesh_item_type) const;
 
 private:
     /// A mapping from property's name to the stored object of any type.