Extend Engine to have Pause, Resume, Cancel operations

[Peter St Clair]

Is your feature request related to a problem? Please describe.
When dealing with large files, it would be good to be able to have to ability to Pause/Continue or Cancel the download.

Describe the solution you'd like
Add some additional methods to the Engine to Pause, Continue and Cancel the download process.

Describe alternatives you've considered
Another suggestion would also be to not implement the Engine as a static class, that way you could support the ability to have multiple concurrent downloads happening at once.

[Greg]

This issue is now resolved. Thank you for the suggestion. I will look into making the Engine non static at a later date, but for now, pause/resume/cancellation support has been added.