keditbookmarks: add standard icons and shortcuts to Undo/Redo actions
Review Request #129423 - Created Nov. 18, 2016 and submitted
These actions are created by QUndoStack in order that it can manage the action text. However, this means that they do not get the standard KDE action icon or shortcuts set. This change sets those by reference to the appropriate KStandardAction.
Built keditbookmarks (split repository master version) with this change, observed correct appearance and operation of Undo/Redo actions.