Update the "TargetFramework" versions

[AdityaNPL]

Since .NET Core 2.0 has reached End of life, we should look to update to .Net core 2.1 which has LTS?
https://dotnet.microsoft.com/download/dotnet-core

At the same time we can look to update the .Net framework version from 4.7 -> 4.8 (recommended) as well?
https://dotnet.microsoft.com/download/dotnet-framework

[alexirion10]

.netcore2.1 is a good upgrade
please leave .net framework 4.7 in place though as we still use 4.7 in several dependent projects