Fix bug in background file writing.

Change-Id: I3ef2aed4363920a13136474c4da5342d58844972
Use a event loop while waiting for a file write to complete.

Change-Id: If6b7df9658c43a4c0839e1ccc9ac01034f902b8a
Use the new QtGui::FileFormatDialog in MainWindow.

Change-Id: I1be62d4e6927821f389cf58c8178300d5a960d37
Merge topic 'mq-open-output' into master

9d4576de Use the new QtGui::FileFormatDialog in MainWindow.
6fad4dfa Use a event loop while waiting for a file write to complete.
a406359b Fix bug in background file writing.