Improve Usability of HDF5 Writing

[maarzt]

Two tiny changes. That I need in Labkit to make the writing of HDF5 convinient for the users.

1. Correctly shut down threads by using try finally block. (In Labkit I throw CancellationException to interrupt the writing of the image. But this caused the threads to no clean up)

2. Fluent progress bar for single timepoint images. Now the progress is shown as planes of the images are written, and writing the meta data will increase progress by 1% (not 50%).

[maarzt]

Thank you for the quick review & merge.