build/build.ps1: Changed to install both 1.0.5 and 2.0.0 .NET Core SDKs, since the former is still required to run tests on .NET Core 1.0
build/build.ps1: Changed to install both 1.0.5 and 2.0.0 .NET Core SDKs, since the former is still required to run tests on .NET Core 1.0

jeme/lucenenet,apache/lucenenet,jeme/lucenenet,apache/lucenenet,laimis/lucenenet,NightOwl888/lucenenet,sisve/lucenenet,sisve/lucenenet,apache/lucenenet,jeme/lucenenet,laimis/lucenenet,jeme/lucenenet,NightOwl888/lucenenet,apache/lucenenet,NightOwl888/lucenenet,NightOwl888/lucenenet