Extend ConvertApiParam for File parameter #2

There is no way how to add more than one file to ConvertApiParam.
Extend ConvertApiParam class to ConvertApiFileParam and accept only one parameter, stream or string. The class will take care of File param names.

Now

new ConvertApiParam("File", File.OpenRead(@"\source\test.docx"))

Extended

new ConvertApiFileParam(File.OpenRead(@"\source\test.docx"))
new ConvertApiFileParam("http://www.mydomain.com/files.doc")