Add a structure to hold undo commands

Add the undocommands.cpp / undocommands.h files, which will hold a
collection of classes that will hold undo commands.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

qt-ui/undocommands.cpp

@@ -0,0 +1,16 @@
+#include "undocommands.h"
+
+UndoDeleteDive::UndoDeleteDive(QList<dive *> diveList)
+{
+
+}
+
+void UndoDeleteDive::undo()
+{
+
+}
+
+void UndoDeleteDive::redo()
+{
+
+}