[i514] Explain purpose of 'onInstrumentChangedByEditor' methods (#514) (Closes #514)

Merging branch 'i514'  into 'main'.

See merge request !1449

GUI/View/Instrument/InstrumentLibraryEditor.cpp

@@ -255,6 +255,8 @@ void InstrumentLibraryEditor::onInstrumentDescriptionEdited(const QString& t)
 
 void InstrumentLibraryEditor::onInstrumentChangedByEditor()
 {
+    // uses 'MultiInstrumentNotifier::instrumentChanged' signal to set
+    // 'InstrumentLibrary:m_modified' flag to true ==> save library on close.
     auto* currentInstrument = m_treeModel->itemForIndex(m_ui->treeView->currentIndex());
     m_instrumentLibrary->editController()->notifyInstrumentChanged(currentInstrument);
 }

GUI/View/Instrument/InstrumentView.cpp

@@ -168,6 +168,9 @@ void InstrumentView::onInstrumentdescriptionEdited(const QString& t)
 
 void InstrumentView::onInstrumentChangedByEditor()
 {
+    // uses 'MultiInstrumentNotifier::instrumentChanged' signal for two purposes:
+    // 1) notify 'ProjectDocument' that user has changed data ==> mark project with '*'
+    // 2) notify 'LinkInstrumentManager' ==> unlink instrument from data if they are incompatible
     m_document->multiNotifier()->notifyInstrumentChanged(
         m_instrumentListView->currentInstrumentItem());
 }