Gui: Add a context menu to select obstructed items (from RT fork)

As the title says, this is from RT's fork. I only adjusted it a little
bit and removed pie selection which was previously in the
implementation.

To activate context menu - "G, G", then if it can't resolve edges vs
faces, it adds QMenus on top to let user decide which one to select.

Co-authored-by: tetektoza <tetektoza@users.noreply.github.com>

src/Gui/Workbench.cpp

@@ -737,7 +737,8 @@ MenuItem* StdWorkbench::setupMenuBar() const
           << "Separator"
           << "Std_ProjectUtil"
           << "Std_DlgParameter"
-          << "Std_DlgCustomize";
+          << "Std_DlgCustomize"
+          << "Std_PickGeometry";
 
     // Macro
     auto macro = new MenuItem( menuBar );