Remove unnecessary items in the right click context menu

[frog23]

When pressing the right mouse button within the identification panel either on the black background, or on a file or on a folder, either before or after the identification was run, the context menu always has the same 6 items in it, the same as in the Edit-Tab of the menu bar. However most of the entries within this context menu are disabled in most of the cases (and sometimes not even that: the entries "Expand" and "Expend next three levels" can always be selected, even they have no action, like when clicking on an individual file).

The context menus should be cleaned up and all the items that are not applicable should be removed instead of disabled (disabling is the right thing to do for the Edit tab in the menu bar, but this is a different UI element with different rules).