Unobserved exception handling

[twometresteve]

Goal

Correctly respond to UnobservedTaskExceptions, in terms of whether the process will be terminated.

Design

• For .NET Framework versions prior to 4.5, the process will always terminate.
• For .NET Framework versions after 4.5, the default behavior is not to terminate, but can be configured to do so. We therefore check for the ThrowUnobservedTaskExceptions configuration.
• For .NET Standard we will assume that the default behavior holds - not to terminate

Tests

Tested with the standard regression tests, together with manual testing using the examples in the repository.

Discussion

Outstanding Questions

Assuming that the process will not terminate with .NET Standard is not ideal, as it could be configured to do so. However, determining how to check the configuration in a portable way has proven troublesome and so we will address this for concrete examples on a case-by-case basis should the need arise. The default behavior is likely to prevail and is catered for, in any case.

Linked issues

Fixes #116