Add a set to know whether a new file is already being uploading. Fixes issue 156
Add a set to know whether a new file is already being uploading. Fixes issue 156

jijo-paulose/gwtupload,jknaresh/gwtupload,manolo/gwtupload,jknaresh/gwtupload,verma-neeraj-in/gwtupload,cyrilmhansen/gwtupload,finderos47/gwtupload-DEF.LV,verma-neeraj-in/gwtupload,tectronics/gwtupload,verma-neeraj-in/gwtupload,jijo-paulose/gwtupload,Elisabitao/gwtupload,cyrilmhansen/gwtupload,mwl/gwt-upload,Elisabitao/gwtupload,Elisabitao/gwtupload,jijo-paulose/gwtupload,cyrilmhansen/gwtupload,Elisabitao/gwtupload,mwl/gwt-upload,finderos47/gwtupload-DEF.LV,jijo-paulose/gwtupload,cyrilmhansen/gwtupload,verma-neeraj-in/gwtupload,manolo/gwtupload,mwl/gwt-upload,manolo/gwtupload,finderos47/gwtupload-DEF.LV,tectronics/gwtupload,finderos47/gwtupload-DEF.LV,tectronics/gwtupload,jknaresh/gwtupload,mwl/gwt-upload,jknaresh/gwtupload,Elisabitao/gwtupload,tectronics/gwtupload,finderos47/gwtupload-DEF.LV,cyrilmhansen/gwtupload,verma-neeraj-in/gwtupload,manolo/gwtupload,jknaresh/gwtupload,jijo-paulose/gwtupload,tectronics/gwtupload,manolo/gwtupload