Issue #207: Add support for e-mail properties from data extract task.
Issue #207: Simplify data extract step labels.
Clean up.
Clean up.
Clean up.

* Remove unused variables.

* Remove redundant comments.

* Simplify conditional expression.

* Use appropriate responder.

* Delegate to Extent#toPolygon().
Fix initial DataExtract widget width/height regression.
Merge branch '#207/support-data-extract-and-email' into develop