LoadOptions for GridWeb

There are some loadoptions we can set before import the file.

we can use GridLoadOptions (for general file) and GridTxtLoadOptions (for csv file)

**load with other encode **

For the csv file, it is actually a text-based file, without the specific encoding described in the xlsx format file.

Therefore, users can set specific character encoding before loading the file.

here is a sample code to load with chinese:

    GridTxtLoadOptions topt = new GridTxtLoadOptions();
    topt.Encoding = (Encoding.GetEncoding("GB2312"));
    GridWeb1.LoadOptions = topt;
    String filePath = Server.MapPath("~/workbook/chinesefile.csv");
    GridWeb1.ImportExcelFile(filePath);