Add libraryPaths array to Project element (.qmlproject format)

Will be passed to qmlviewer with the "-L" option. Storing this in
the .qmlproject file format itself (and not in the .user file) is useful
in case the libraries are relative/part of the checkout that is shared
between users/computers.

src/plugins/qmlprojectmanager/fileformat/qmlprojectitem.cpp

@@ -9,6 +9,7 @@ class QmlProjectItemPrivate : public QObject {
 
 public:
     QString sourceDirectory;
+    QStringList libraryPaths;
 
     QList<QmlFileFilterItem*> qmlFileFilters() const;
 
@@ -78,6 +79,23 @@ void QmlProjectItem::setSourceDirectory(const QString &directoryPath)
     emit sourceDirectoryChanged();
 }
 
+QStringList QmlProjectItem::libraryPaths() const
+{
+    const Q_D(QmlProjectItem);
+    return d->libraryPaths;
+}
+
+void QmlProjectItem::setLibraryPaths(const QStringList &libraryPaths)
+{
+    Q_D(QmlProjectItem);
+
+    if (d->libraryPaths == libraryPaths)
+        return;
+
+    d->libraryPaths = libraryPaths;
+    emit libraryPathsChanged();
+}
+
 /* Returns list of absolute paths */
 QStringList QmlProjectItem::files() const
 {