Add `ActivityWithErrorHandler.cs`

[martinkearn]

A file called ActivityWithErrorHandler.cs is seen in most of the preview samples which seems to add basic error handling to the adapter. It is in enough samples that it seems like a v4.3 pattern.

Here it is in the Core Bot sample: https://github.com/Microsoft/BotBuilder-Samples/blob/samples-work-in-progress/samples/csharp_dotnetcore/13.core-bot/AdapterWithErrorHandler.cs

Need to work this file into the StarterBot template

[martinkearn]

@daltskin, is this fixed in 8326554