Allow update track rating in DataListView

Summary

Allow changing tracks rating from DataListView.

Details

Currently, correct me if I'm wrong, to update tracks rating we need to edit track's details, click. modify and then confirm the change. I really would like to edit the rating on the DataListView.

This change includes:

• RatingStar editable to true in ListBrowserDelegate (it only affects when desktop)

• New signal on ListBrowserDelegate

  signal trackRatingChanged(var url, var rating)

• DataListView connects previous signal and calls ElisaApplication.musicManager.updateSingleFileMetaData

Pending/Probably wrong things

• DataListView should use DataTypes.ColumnRoles.RatingRole instead of fixed magic number.

    function updateRating(url, rating) {
        // TODO: Use DataTypes::ColumnsRoles instead of 272
        ElisaApplication.musicManager.updateSingleFileMetaData(url, ColumnsRoles.RatingRole, rating)
    }

• I exported tracksListener->updateSingleFileMetaData through MusicListenersManager to allow call it from qml (ElisaApplication.musicManager.updateSingleFileMetaData), I suppose there is currently some way to call it but I couldn't find it.

Please excuse me if this is not the correct way to create a merge request or if I have skipped any step, but I really would like to have this feature :)