Long overdue changes and refactoring for qemu handling.

Fixes: - react on build/ run configuration changes
       - now notices environment changes, like switching Qt versions
       - start button is now only shown if we have a valid qemu runtime
       - enabled/ disabled state works properly when loading a project

Task-number: QTCREATOR-210, QTCREATORBUG-1252, QTCREATORBUG-1082
Reviewed-by: ck

src/plugins/qt4projectmanager/qt4projectmanagerplugin.h

@@ -56,6 +56,7 @@ class QMakeStepFactory;
 class MakeStepFactory;
 class EmbeddedPropertiesPage;
 class GettingStartedWelcomePage;
+class MaemoManager;
 
 class Qt4ProjectManagerPlugin : public ExtensionSystem::IPlugin
 {
@@ -85,6 +86,7 @@ private:
     ProjectExplorer::ProjectExplorerPlugin *m_projectExplorer;
     ProFileEditorFactory *m_proFileEditorFactory;
     Qt4Manager *m_qt4ProjectManager;
+    MaemoManager *m_maemoManager;
 
     int m_projectContext;