appveyor install nsis from s3 (#3212)
appveyor install nsis from s3 (#3212)

* appveyor install nsis from s3

* Pass YAML linting, pls work

* Simpler nsis download scheme

CornerOfSkyline/qgroundcontrol,CornerOfSkyline/qgroundcontrol,CornerOfSkyline/qgroundcontrol,kd0aij/qgroundcontrol,RedoXyde/PX4_qGCS,mihadyuk/qgroundcontrol,mihadyuk/qgroundcontrol,kd0aij/qgroundcontrol,ethz-asl/qgc_asl,Hunter522/qgroundcontrol,CornerOfSkyline/qgroundcontrol,mihadyuk/qgroundcontrol,Hunter522/qgroundcontrol,CornerOfSkyline/qgroundcontrol,mihadyuk/qgroundcontrol,RedoXyde/PX4_qGCS,RedoXyde/PX4_qGCS,Hunter522/qgroundcontrol,RedoXyde/PX4_qGCS,CornerOfSkyline/qgroundcontrol,RedoXyde/PX4_qGCS,kd0aij/qgroundcontrol,Hunter522/qgroundcontrol,ethz-asl/qgc_asl,RedoXyde/PX4_qGCS,Hunter522/qgroundcontrol,ethz-asl/qgc_asl,kd0aij/qgroundcontrol,ethz-asl/qgc_asl,mihadyuk/qgroundcontrol,kd0aij/qgroundcontrol,ethz-asl/qgc_asl,mihadyuk/qgroundcontrol,Hunter522/qgroundcontrol,kd0aij/qgroundcontrol