Added some class descriptions and Doxygen config.

explaintreemodelitem.h

@@ -21,6 +21,9 @@ typedef std::shared_ptr<ExplainTreeModelItem> ExplainTreeModelItemPtr;
  * 4. rows
  * 5. loops
  */
+
+/** \brief Model class for displaying the explain of a query in a tree like format.
+ */
 class ExplainTreeModelItem: public std::enable_shared_from_this<ExplainTreeModelItem> {
 public:
 	typedef std::shared_ptr<ExplainTreeModelItem> ItemPtr;