Enable Rx for upload application

The upload application now use Reactive Extensions (Rx) instead of a
BlockingCollection for passing string messages between the UI and the
FileUpload class.

Also enabled in this commit is ISubject properties for upload latency,
latest synchronization time and measurements uploaded.  The UI has been
updated to include a small dashboard that displays the latest latency
and synchronization time.
Azure service perform InsertOrReplace

The Azure web service now runs an InsertOrReplace batch operation
instead of an Insert operation.

This approach is the absolutely simplest way to support the scenario
where the client forgets the latest synchronization time.