add dotnet installation in appveyor
add dotnet installation in appveyor

bvenn/BioFSharp,HLWeil/BioFSharp,bvenn/BioFSharp,CSBiology/BioFSharp,CSBiology/BioFSharp,HLWeil/BioFSharp,bvenn/BioFSharp,HLWeil/BioFSharp,HLWeil/BioFSharp,muehlhaus/BioFSharp