Themed Icons: Introduce Utils::Icon

Instead of describing icons via file name or in the themed icons case
via
a string that is a list of mask/color pairs, we have now a class for it.

Icons are now listed in per-plugin *icons.h headers.

RunControl::m_icon was The only place left where an icon property was in
fact a string. This patch changes that member to be a Utils::Icon.

Change-Id: Ibcfa8bb25e6d2e330c567ee7ccc0b97ead603177
Reviewed-by: Eike Ziller <eike.ziller@theqtcompany.com>

src/plugins/git/gitplugin.cpp

@@ -49,6 +49,7 @@
 
 #include <coreplugin/icore.h>
 #include <coreplugin/coreconstants.h>
+#include <coreplugin/coreicons.h>
 #include <coreplugin/documentmanager.h>
 #include <coreplugin/actionmanager/actionmanager.h>
 #include <coreplugin/actionmanager/actioncontainer.h>
@@ -721,7 +722,7 @@ class RebaseItemDelegate : public IconItemDelegate
 {
 public:
     RebaseItemDelegate(LogChangeWidget *widget)
-        : IconItemDelegate(widget, QLatin1String(Core::Constants::ICON_UNDO))
+        : IconItemDelegate(widget, Core::Icons::UNDO.imageFileName())
     {
     }