Added initial support for directory based packages in class diagrams

tests/t00065/module1/module1.h

@@ -0,0 +1,11 @@
+#include "submodule1a/submodule1a.h"
+
+#pragma once
+
+namespace clanguml {
+namespace t00065 {
+struct A {
+    detail::AImpl *pimpl;
+};
+}
+}

tests/t00065/module1/submodule1a/submodule1a.h

@@ -0,0 +1,9 @@
+#pragma once
+
+namespace clanguml {
+namespace t00065 {
+namespace detail {
+struct AImpl { };
+}
+}
+}