Column reordering breaks types used for sorting

[gilthe]

This is with a recently downloaded:

 * Included libraries:
 *   JSZip 3.10.1, pdfmake 0.2.7, DataTables 2.1.8, Buttons 3.2.0, Column visibility 3.2.0, HTML5 export 3.2.0, Print view 3.2.0, ColReorder 2.0.4, KeyTable 2.12.1, Scroller 2.4.3

After column reordering, all columns sort like string (the default) even though they were initialized with, e.g., "num". Before reordering, all sorting works as expected.
It took me a while to find this, but in the function:

/**
 * Run finishing activities after one or more columns have been reordered.
 *
 * @param dt DataTable being operated on - must be a single table instance
 */
function finalise(dt) {
    // Cache invalidation. Always read from the data object rather
    // than reading back from the DOM since it could have been
    // changed by a renderer
    dt.rows().invalidate('data');
    // Redraw the header / footer. Its a little bit of a hack this, as DT
    // doesn't expose the header draw as an API method. It calls state
    // saving, so we don't need to here.
    dt.column(0).visible(dt.column(0).visible());
    dt.columns.adjust();
    dt.columns().types(); // !!!!!! ADDED !!!!!!!
    // Fire an event so other plug-ins can update
    var order = dt.colReorder.order();
    dt.trigger('columns-reordered', [
        {
            order: order,
            mapping: invertKeyValues(order)
        }
    ]);
}

The call to rows().invalidate() also invalidates columns, including their types (sType becomes null). To rectify the behavior in my case, I inserted an extra call to columns.types().

[AllanJard]

Hi - many thanks for this and apologies for the delayed reply. I actually think the issue goes a little deeper and DataTables should resolve the data types for the columns on ordering if needed. I've committed that fix here.