Creates an Excel spreadsheet from a data string
@memberof TableExport.prototype
@param data {String}
@param merges {Object[]}
function(data, merges) {
      var ws = {};
      var range = { s: { c: 10000000, r: 10000000 }, e: { c: 0, r: 0 } };
      var types = this.typeConfig;
      for (var R = 0; R !== data.length; ++R) {
        for (var C = 0; C !== data[R].length; ++C) {
          if (range.s.r > R) range.s.r = R;
          if (range.s.c > C) range.s.c = C;
          if (range.e.r < R) range.e.r = R;
          if (range.e.c < C) range.e.c = C;
          var cell = data[R][C];
          if (!cell || !cell.v) continue;
          var cell_ref = XLSX.utils.encode_cell({ c: C, r: R });

          if (!cell.t) {
            if (types.number.assert(cell.v)) cell.t = _TYPE.NUMBER;
            else if (types.boolean.assert(cell.v)) cell.t = _TYPE.BOOLEAN;
            else if (types.date.assert(cell.v)) cell.t = _TYPE.DATE;
            else cell.t = _TYPE.STRING;
          }
          if (cell.t === _TYPE.DATE) {
            cell.t = _TYPE.NUMBER;
            cell.z = XLSX.SSF._table[14];
            cell.v = this.dateNum(cell.v);
          }
          ws[cell_ref] = cell;
        }
      }
      ws["!merges"] = merges;
      if (range.s.c < 10000000) ws["!ref"] = XLSX.utils.encode_range(range);
      return ws;
    }