Add total segment count to progress callback

Signed-off-by: Simon Marchi <simon.marchi@polymtl.ca>
Qt: Connect download_manager to downloads table (very basic)

Signed-off-by: Simon Marchi <simon.marchi@polymtl.ca>
Qt: pep8

Signed-off-by: Simon Marchi <simon.marchi@polymtl.ca>