Add a id() method to projects

* This makes it easier to distinguish projects in the
   userfileaccessor

src/plugins/qmlprojectmanager/qmlproject.cpp

@@ -226,6 +226,11 @@ QString QmlProject::displayName() const
     return m_projectName;
 }
 
+QString QmlProject::id() const
+{
+    return QLatin1String("QmlProjectManager.QmlProject");
+}
+
 Core::IFile *QmlProject::file() const
 {
     return m_file;

src/plugins/qmlprojectmanager/qmlproject.h

@@ -159,6 +159,7 @@ public:
     QString filesFileName() const;
 
     virtual QString displayName() const;
+    virtual QString id() const;
     virtual Core::IFile *file() const;
     virtual Internal::Manager *projectManager() const;
     virtual ProjectExplorer::IBuildConfigurationFactory *buildConfigurationFactory() const;