ProjectExplorer: Icon for enabling kits in the project mode

Disabled kit icon plus small "+" overlay.

Change-Id: I58df0da662baf9977382733e8d003766bd232281
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>

src/libs/utils/utilsicons.cpp

@@ -181,6 +181,9 @@ const Icon COLLAPSE({
 const Icon COLLAPSE_TOOLBAR({
         {QLatin1String(":/utils/images/collapse.png"), Theme::IconsBaseColor}});
 const Icon EMPTY14(":/utils/images/empty14.png");
+const Icon ENABLE_KIT_OVERLAY({
+        {":/projectexplorer/images/enablekitbackground.png", Theme::IconsRunColor},
+        {":/projectexplorer/images/enablekitforeground.png", Theme::BackgroundColorNormal}}, Icon::Tint);
 
 } // namespace Icons
 } // namespace Utils