Qt4projectManager: Refactor Qt4Target, split up in per target classes

Almost(*) all of the symbian and maemo specific code is now theoretically
moveable to a separate plugin. Thus making it possible to implement
new targets in a plugin.

(*) Noteable missing is the qtversion, which needs to be split up
per target too.

Also fixes
Task-Nr: QTCREATORBUG-2440

Reviewed-By: hunger
Reviewed-By: ck

src/plugins/qmlprojectmanager/qmlproject.cpp

@@ -58,7 +58,6 @@ QmlProject::QmlProject(Internal::Manager *manager, const QString &fileName)
       m_modelManager(ExtensionSystem::PluginManager::instance()->getObject<QmlJS::ModelManagerInterface>()),
       m_fileWatcher(new ProjectExplorer::FileWatcher(this))
 {
-    setSupportedTargetIds(QSet<QString>() << QLatin1String(Constants::QML_VIEWER_TARGET_ID));
     QFileInfo fileInfo(m_fileName);
     m_projectName = fileInfo.completeBaseName();