The attribute start_index is not read from file

[mooiman]

Some variables on a UGRID file contain the indices of an array, these indices are zero- or one-based. The value of the start_index (0/1) determines if the array on file is zero- or one-based. Depending on the language which uses the UGrid-library the indices should be corrected by the start_index. Therefor the start_index should be read from file. Example: C++ uses zero-based indices and Fortran uses one-based indices.

For a 1D mesh I use the code:
`
{
// reading start_index, needed for edge_nodes array
int i_var;
int start_index = -2;
std::string var_edge_node;
std::string var_start_index;
std::string tmp_name(stripSpaces(m_mesh1d.name));
status = get_attribute_by_var_name(m_ncid, tmp_name, "edge_node_connectivity", &var_edge_node);
status = nc_inq_varid(m_ncid, var_edge_node.c_str(), &i_var);
status = nc_get_att_int(m_ncid, i_var, "start_index", &start_index);
m_mesh1d.start_index = start_index;

        if (m_mesh1d.start_index != 0)
        {
            for (int i = 0; i < m_mesh1d.num_edges * 2; ++i)
            {
                m_mesh1d.edge_node[i] -= m_mesh1d.start_index;
            }
        }
    }