[Gui] ActionGroup can declared being a "Mode" action

This will essentially not update the tooltip when an action is checked as it isn't suitable
As example, view DrawStyle command where the group tooltip is better than the selected action tooltip

Only UserEditMode is implemented in this commit, should be pushed to DrawStyle and maybe other after merge

src/Gui/Action.cpp

@@ -227,7 +227,7 @@ void Action::setMenuRole(QAction::MenuRole menuRole)
  * to the command object.
  */
 ActionGroup::ActionGroup ( Command* pcCmd,QObject * parent)
-  : Action(pcCmd, parent), _group(0), _dropDown(false),_external(false),_toggle(false)
+  : Action(pcCmd, parent), _group(0), _dropDown(false),_external(false),_toggle(false),_isMode(false)
 {
     _group = new QActionGroup(this);
     connect(_group, SIGNAL(triggered(QAction*)), this, SLOT(onActivated (QAction*)));
@@ -336,7 +336,7 @@ void ActionGroup::setCheckedAction(int i)
     QAction* a = _group->actions()[i];
     a->setChecked(true);
     this->setIcon(a->icon());
-    this->setToolTip(a->toolTip());
+    if (!this->_isMode) this->setToolTip(a->toolTip());
     this->setProperty("defaultAction", QVariant(i));
 }
 
@@ -378,7 +378,7 @@ void ActionGroup::onActivated (QAction* a)
     }
 #endif
     this->setIcon(a->icon());
-    this->setToolTip(a->toolTip());
+    if (!this->_isMode) this->setToolTip(a->toolTip());
     this->setProperty("defaultAction", QVariant(index));
     _pcCmd->invoke(index, Command::TriggerChildAction);
 }

src/Gui/Action.h

@@ -107,6 +107,7 @@ public:
     void setExclusive (bool);
     bool isExclusive() const;
     void setVisible (bool);
+    void setIsMode(bool b) { _isMode = b; }
 
     void setDropDownMenu(bool b) { _dropDown = b; }
     QAction* addAction(QAction*);
@@ -126,6 +127,7 @@ protected:
     bool _dropDown;
     bool _external;
     bool _toggle;
+    bool _isMode;
 };
 
 // --------------------------------------------------------------------

src/Gui/CommandStd.cpp

@@ -850,6 +850,7 @@ Gui::Action * StdCmdUserEditMode::createAction(void)
 {
     Gui::ActionGroup* pcAction = new Gui::ActionGroup(this, Gui::getMainWindow());
     pcAction->setDropDownMenu(true);
+    pcAction->setIsMode(true);
     applyCommandData(this->className(), pcAction);
     
     for (auto const &uem : Gui::Application::Instance->listUserEditModes()) {