Expose TPL methods, either instance or extensions

[tsahi]

Is your feature request related to a problem? Please describe.
DAAB exposes the older APM async programming model, using BeginXXX() - EndXXX(). We should expose Task Parallel Library methods using async/await, exposing the TPL API added to ADO.NET.

Describe the solution you'd like
Expose TPL methods from the Database abstract class

Describe alternatives you've considered
We could wrap the APM methods using Task.Factory.FromAsync(), but that would only wrap the existing methods. It would be more efficient to access the ADO.NET methods directly.