Add support for OperationCancelledException and TaskCancelledException

[krajek]

Continuation of #65, closes #64

I will first cleanup style-cop warnings and tests, then add new tests and complete PR.
Work in progress.

[RehanSaeed]

wonderful

[krajek]

@Shatl and @RehanSaeed could you please take a last look on the PR?

Note, that I had to remove the usage of destructureException function for Task.Exception destructuring because it caused a stack overflow exception in case of cyclic references in the object graph. The reason is that destructuringObjects dictionary, that tracks already destructured objects was created once again for each new inner exception. Moreover, using destructureException would be incompatible with the rest of the reflection-based destructuring.

[RehanSaeed]

Only one comment, otherwise LGTM.