Apply sensitivity label to document

[xaaron]

I use excelize to generate reports. Recently there is a need to label the sensitivity of these reports. In Excel you do this by going to HOME->Sensitivity-[choose sensitivity leve]

My request to be able to do this through Excelize. Something like:

f, err := excelize.OpenFile(filename)
if err != nil {
  f.SetSensitivity(sensitivity value)
}