Update BuildAndTest.proj to create packages.
Update BuildAndTest.proj to create packages.

This updates BuildAndTest.proj to build Packages.proj, which will in
turn build all the packaging projects and create NuGet packages.

genlu/roslyn-analyzers,natidea/roslyn-analyzers,mattwar/roslyn-analyzers,SpotLabsNET/roslyn-analyzers,mavasani/roslyn-analyzers,dotnet/roslyn-analyzers,heejaechang/roslyn-analyzers,jaredpar/roslyn-analyzers,srivatsn/roslyn-analyzers,pakdev/roslyn-analyzers,bkoelman/roslyn-analyzers,qinxgit/roslyn-analyzers,dotnet/roslyn-analyzers,pakdev/roslyn-analyzers,jasonmalinowski/roslyn-analyzers,VitalyTVA/roslyn-analyzers,tmeschter/roslyn-analyzers-1,modulexcite/roslyn-analyzers,jinujoseph/roslyn-analyzers,Anniepoh/roslyn-analyzers,mavasani/roslyn-analyzers,jepetty/roslyn-analyzers