Randomize names of uploaded files

1. add public "\kUploadHelper::randomizeFilename($filename)" method, that will: - 0.5h
   1. generate random 16 byte string using "SecurityGenerator::generateBytes(8)" method call
   2. inject it in here "{file_name}_{random_string}.{file_extension}"
2. in the "\kUploadHelper::getUploadedFilename" method wrap response with "\kUploadHelper::randomizeFilename" method call - 0.3h
3. in the "\kUploadFormatter::_processRegularUploader" method, when file was uploaded (the error is UPLOAD_ERR_OK) but before any validation happens wrap "$value['name']" with  "\kUploadHelper::randomizeFilename" method call - 0.2h

Quote: 1h*1.4=1.5h