Wizards: allows filtering of wizards based on Qt version

Every wizard now implements requiredFeatures() to define a feature set.
If the feature set is not satisfied by the available Qt Versions,
the wizard is not shown in the create file/project dialog.

Every Qt version can define the provided feature set in availableFeatures()
defined in BaseQtVersion.

Change-Id: Ie9e2c210d19187b2296451948c36d274f2096623
Reviewed-by: Daniel Teske <daniel.teske@nokia.com>
Reviewed-by: Alessandro Portale <alessandro.portale@nokia.com>

src/plugins/qt4projectmanager/wizards/emptyprojectwizard.cpp

@@ -52,6 +52,11 @@ EmptyProjectWizard::EmptyProjectWizard()
 {
 }
 
+Core::FeatureSet EmptyProjectWizard::requiredFeatures() const
+{
+    return Core::FeatureSet();
+}
+
 QWizard *EmptyProjectWizard::createWizardDialog(QWidget *parent,
                                               const QString &defaultPath,
                                               const WizardPageList &extensionPages) const