Make the welcome screen into plugins.

This removes the all hard dependencies to and from welcome screen,
except the one to the core plugin. More in detail:

- Add IWelcomePage to add a tab to the welcome screen
- Move tabs in the modules where they belong
- Enables QHelpManager to open help fullscreen and contextually
- "Getting Started" moves to Qt4ProjectManager
- Projects & Sessions (aka "Develop") moves to ProjectExplorer
- "Community" remains in the welcome plugin for simplicity

src/plugins/qt4projectmanager/qt4projectmanagerplugin.cpp

@@ -44,6 +44,8 @@
 #include "qtversionmanager.h"
 #include "qtoptionspage.h"
 #include "externaleditors.h"
+#include "gettingstartedwelcomepage.h"
+#include "gettingstartedwelcomepagewidget.h"
 
 #ifdef QTCREATOR_WITH_S60
 #include "qt-s60/s60manager.h"
@@ -82,6 +84,8 @@ Qt4ProjectManagerPlugin::~Qt4ProjectManagerPlugin()
     delete m_proFileEditorFactory;
     removeObject(m_qt4ProjectManager);
     delete m_qt4ProjectManager;
+    removeObject(m_welcomePage);
+    delete m_welcomePage;
 }
 /*
 static Core::Command *createSeparator(Core::ActionManager *am,
@@ -106,9 +110,16 @@ bool Qt4ProjectManagerPlugin::initialize(const QStringList &arguments, QString *
     m_projectExplorer = ProjectExplorer::ProjectExplorerPlugin::instance();
     Core::ActionManager *am = core->actionManager();
 
-    addAutoReleasedObject(new QtVersionManager());
+    QtVersionManager *mgr = new QtVersionManager();
+    addAutoReleasedObject(mgr);
     addAutoReleasedObject(new QtOptionsPage());
 
+    m_welcomePage = new GettingStartedWelcomePage;
+    addObject(m_welcomePage);
+    GettingStartedWelcomePageWidget *gswp =
+            static_cast<GettingStartedWelcomePageWidget*>(m_welcomePage->page());
+    connect(mgr, SIGNAL(updateExamples(QString,QString,QString)),
+            gswp, SLOT(updateExamples(QString,QString,QString)));
 
     //create and register objects
     m_qt4ProjectManager = new Qt4Manager(this);