Updated doxyfile to a modern version

- From version 1.5 to 1.8
- Added lateral pannel
- Clickable inheritance/collaboration diagrams

Author: cesaro

.gitignore

@@ -112,3 +112,6 @@ src/util/irep_ids_convert
 src/util/irep_ids_convert.exe
 
 *.pyc
+
+# auto generated documentation
+doc/html/