Analyze memory write operations

[FriedrichFroebel]

Running didjvu bundle -o out.djvu *.tif on a directory which contains 413 images with a total size of 58 MB results in an output file of size 12 MB. The task monitor reports about 12.5 GB of write operations for the didjvu process at the end, which is more than 200 times the input size.

This seems to be quite some overhead which might receive some further analysis on which operations cause this and whether there is anything we can optimize here.

The above observations were made with some older commit of this repository running on Python 3.6.