Migrate samples from the "sample" branch in dotnet/try

[BillWagner]

We've created this repo because the dotnet/try repository is the wrong location.

There are a few subtasks for completing this:

• Bring the C# 8 exploration to this repository (See Migrate explore C# 8 to try-samples repo #7)
• Bring the beginners samples and Pascal's triangle sample to this repo. Source is in the dotnet/try#Samples branch.
• Update the last item in the dotnet/try README section on "getting started" to point to this repo.
• Delete the "Samples" branch from the dotnet/try repo.

/cc @LadyNaggaga @jonsequitur

[BillWagner]

All tasks have been completed. Closing this.