Resolve issues with Track3P download and display

Fixes a number of issues that were uncovered testing Track3P examples

• Adds a queue for multiple download requests. The qtNewtDownloadRequester doesn't support concurrent requests, and we have essentially been lucky until now. (As developers, we usually do partial downloads.)
• Adds progress dialog to job downloads. Track3P downloads, in particular, can take minutes, so some feedback is warranted.
• Fixes some peculiar behavior displaying Track3P particle data, in which the pipeline-setup code sometimes uses the view displaying the smtk model resource instead of creating a second view.
• Also updates qtJobsModel::onJobAdded() to do a full model reset instead inserting the relevant row. The current logic modifies the project before calling this method, which can screw up the display. Doing a brute force reset seems to keep things sync'd up.
• Also adds logic to intercept application close event and deal with modified project.