[InteractiveSegmentation] Decouple progress bar & more

[dboun]

Fix #142 progress bar resetting

Fix #115 Remove QProgressBar from module

(Also includes PR #141 and PR #145 to avoid conflicts. Please review these two PRs first) (sorry for the big PR in general!)

Changelog:

• ProgressBar and Qt Widgets in general are completely decoupled from the module
• Results (ok, errorMessage, result) are returned to the plugin, and it's now the plugin that adds them to the data storage etc + displays the error QMessageBox(es)
• Adding/removing Image nodes (and not LabelSetImage or helper obj etc) resets the progress bar if the algorithm is not running
• Run button is disabled while the algorithm runs, and displays "Running...".
• Fixed a bug introduced recently where InteractiveSegmentation would crash if there was an internal error, like i.e. only 1 label existed in the seeds, because it tried to copy the seeds labelset to the non-existent output segmentation

[ashishsingh18]

Please add some comments

[dboun]

done

[ashishsingh18]

What is the difference between the 2 update methods?

[dboun]

Instead of connecting the ProgressUpdate(int) signal, with the QProgressBar's setValue(int) slot, we connect it with OnProgressUpdateInternalReceived(int), which then emits the signal. This re-emitted signal gets connected with the progress bar in the plugin.

That intermediate stage happens because the initial ProgressUpdate(int) signal doesn't belong to the class captk::InteractiveSegmentation, but a class it uses, so we can't connect it directly.