Sort indicator arrows added to list view in main view.
Fix to sort function: Should no longer only sort by name.
Undo/redo manager added.
Undo and redo options added to edit menu.
Undo and redo functionality added for vertical sorting to the list view of the main view.
Replaced sort button with as sort drop down-menu for clipboard.
Added undo/redo support for clipboard.
Fixed warnings.
Merge pull request #1 from markusmattfolkstenberg/4.2-release

4.2 release