ProjectExplorer: Filter out unusable kits

As side-effect, fix missing expansion of subitems in some cases.

Task-number: QTCREATORBUG-17110
Change-Id: Ib0c74e968d6d814f9dadbb37b323c8ac68cda310
Reviewed-by: Robert Loehning <robert.loehning@qt.io>
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/projectexplorer/projectwindow.h

@@ -42,6 +42,7 @@ enum {
     ItemActivatedFromBelowRole,   // A subitem gots activated and gives us the opportunity to adjust
     ItemActivatedFromAboveRole,   // A parent item gots activated and makes us its active child.
     ItemDeactivatedFromBelowRole, // A subitem got deactivated and gives us the opportunity to adjust
+    ItemUpdatedFromBelowRole,     // A subitem got updated, re-expansion is necessary.
     ActiveItemRole,               // The index of the currently selected item in the tree view
     PanelWidgetRole               // This item's widget to be shown as central widget.
 };