Qt: Add preferences dialog

Signed-off-by: Simon Marchi <simon.marchi@polymtl.ca>
Qt: Prepare code for use of proxy

Signed-off-by: Simon Marchi <simon.marchi@polymtl.ca>
Allow JsonTransport to use a proxy

Signed-off-by: Simon Marchi <simon.marchi@polymtl.ca>
Qt: Create QTouTvConfig object, does nothing for now

Warning, completely untested !

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