UI: Update tab order in the Generate Trace dialog
UI: Change user interaction to obtain snapshots from a loaded trace
* Single-click on API call will no longer take a snapshot
* Double-click on API call _will_ take a snapshot
* Pressing [Enter] while an API call is selected _will_ take a snapshot
* There is a now also a semi-transparent overlay that appears on the state viewing area when there is no current snapshot to view. If there is a trace file loaded, the overlay will contain a big button that says "Click here to snapshot state", which does as expected.

The code to handle the overlay widget and transparency is based on code from: http://stackoverflow.com/questions/19383427/blur-effect-over-a-qwidget-in-qt