Gen2 DataPlaneClient targets dotnet 4.7.2

[xtellurian]

This issue is for a: (mark with an x)

- [ ] bug report -> please search issues before submitting
- [x ] feature request
- [ ] documentation issue or request
- [ ] regression (a behavior that used to work and stopped in a new release)

Minimal steps to reproduce

Look in gen2-sample/csharp-tsi-gen2-sample/DataPlaneClient/DataPlaneClient.csproj

See TargetFrameworkVersion

Expected/desired behavior

Data Plain Client should target the minimum required netstandard version.

Mention any other details that might be useful

Please please please use netstandard. I'm forking this repo so that I can publish a Nuget package (even though we all want you folks to do it)(see #21)

[xtellurian]

See this .csproj file in my netstandard branch

https://github.com/xtellurian/Azure-Time-Series-Insights/blob/netstandard/gen2-sample/csharp-tsi-gen2-sample/DataPlaneClient/DataPlaneClient.csproj

this builds using dotnet build on Mac OS, and because it's netstandard, you can publish the result to NuGet and anybody can consume it.

@yeskarthik can you help with this?

[xtellurian]

#23