add new presentation and remove those who cannot come
add new presentation and remove those who cannot come

AvidGeo/foss4g2017-dev,artardif/foss4g2017-dev,artardif/foss4g2017-dev,AvidGeo/foss4g2017,AvidGeo/foss4g2017-dev,AvidGeo/foss4g2017-dev,AvidGeo/foss4g2017,AvidGeo/foss4g2017,artardif/foss4g2017-dev