Export results tabulated in popup

[KRLango]

This is for issue #749. It presents the results of exports in a popup showing which succeeded and which failed. For failed exports any error message is shown.

An option to open the folder where the exports are saved is also included for quickly getting to the outputs.

[Ion-e]

Bug - Attempting to export an invalid export is reported as "success" in the dialog, however the export doesn't complete, please also note that there are no error messages thrown on the Outputs when the export fails.

Please also note that there no error messages thrown on the Outputs when the export succeeds, is this something we would want? @cmeyer

[cmeyer]

Merged with changes.json, squashed, minor edit to commit message 899098e

Notes and future work:

• You can get the UserInterface ui object using document_controller.ui. This fact isn't always used consistently in existing code...
• Another note: document_controller is basically the window. It is named "controller" due to historical reasons.
• The results dialog should probably be cleaned up to be centered after display (not sure how to do this, may need to measure outputs before-hand and estimate width).
• The results dialog should also probably include a scroll area in case there are 100 output items to report.
• An additional task is to move the "open file in explorer" code to Utility.py so it is common. It occurs in 3+ places right now.
• I didn't add new issues for any of the "to-do" style items above.

[cmeyer]

Bug - Attempting to export an invalid export is reported as "success" in the dialog, however the export doesn't complete, please also note that there are no error messages thrown on the Outputs when the export fails.

Please also note that there no error messages thrown on the Outputs when the export succeeds, is this something we would want? @cmeyer

The Output window is used inconsistently right now - so I'd say let's not worry about it for now until we have a consistent story for the Output window.