#77 Remove "Edit Clipboard" and "Clear" from the history list

[Rudolph]

In qlipper there are only the copied items in the history list, and nothing else. I prefer this kind of view.
"Edit Clipboard" and "Clear" could be placed in the context menu of the parcellite icon that is located in the panel, just below "About", "Save as", and "Preferences", so above "Quit".