Add documentation to skill memory gui

This MR is to be merged into feature/skillMemoryGUI, as major changes there are not yet merged into master. If they are, I will close this MR and open another for master.

source/RobotAPI/libraries/skills_gui/executions/SkillExecutionTreeWidget.cpp

@@ -14,7 +14,7 @@ namespace armarx::skills::gui
     SkillExecutionTreeWidget::runContextMenu(const QPoint& pos)
     {
         // sanity check
-        ARMARX_CHECK(selectionValid());
+        ARMARX_CHECK(selectedExecution.valid());
 
         QMenu* menu = new QMenu();
 
@@ -48,15 +48,22 @@ namespace armarx::skills::gui
     void
     SkillExecutionTreeWidget::stopSelectedExecution()
     {
-        if (!selectionValid())
+        if (!selectedExecution.valid())
             return;
         memory->stopExecution(this->selectedExecution.skillExecutionId);
     }
 
+    bool
+    SkillExecutionTreeWidget::SelectedExecution::valid()
+    {
+        return this->skillExecutionId.skillId.skillName != skills::SkillID::UNKNOWN &&
+               this->skillExecutionId.executionStartedTime.isValid();
+    }
+
     void
     SkillExecutionTreeWidget::rerunSkillWithSimilarParams()
     {
-        if (!selectionValid())
+        if (!selectedExecution.valid())
             return;
         // we don't want to hold state in the gui, so we need to get the parameters from memory:
         skills::SkillExecutionID currentExecutionId = this->selectedExecution.skillExecutionId;
@@ -116,12 +123,6 @@ namespace armarx::skills::gui
                 &SkillExecutionTreeWidget::executionSelectionChanged);
     }
 
-    inline bool
-    SkillExecutionTreeWidget::selectionValid()
-    {
-        return selectedExecution.skillExecutionId.skillId.skillName != skills::SkillID::UNKNOWN;
-    }
-
     void
     SkillExecutionTreeWidget::executionSelectionChanged(QTreeWidgetItem* current,
                                                         QTreeWidgetItem* previous)