Merge a list of Catalogs.

    Parameters:
    -----------
    catalog_list : List of Catalog objects.

    Returns:
    --------
    catalog      : Combined Catalog object

def mergeCatalogs(catalog_list):
    """
    Merge a list of Catalogs.

    Parameters:
    -----------
    catalog_list : List of Catalog objects.

    Returns:
    --------
    catalog      : Combined Catalog object 
    """
    # Check the columns
    for c in catalog_list:
        if c.data.dtype.names != catalog_list[0].data.dtype.names:
            msg = "Catalog data columns not the same."
            raise Exception(msg)
    data = np.concatenate([c.data for c in catalog_list])
    config = catalog_list[0].config
    return Catalog(config,data=data)