Simplified plotting routine for averageLine and averageSmoothLine

Avoid multiple reinitialization.

Signed-off-by: Nicola Ferralis <feranick@hotmail.com>
Added possibility to show legend on plot (through checkbox)

Greatly improved beam recognition.

Signed-off-by: Nicola Ferralis <feranick@hotmail.com>
Updated Changelog.

Signed-off-by: Nicola Ferralis <feranick@hotmail.com>