v1.20 - Storage values in snapshots, Storage edit form and picture

Main improvements:
- Storage: Free space and Total space are now saved with collection snapshots, the Statistics screen can then show both Catalog and Storage data on one graph.
- Storage: A form is now available to edit device fields more easily
- Storage: A picture of the device can be displayed. For now, it must be put in an /images folder in the collection folder, name should be the same as the ID, and the extension should always be .jpg (although any type of image can be read). Example: for a device ID "6", the file path should be "/collection_folder/images/6.jpg"

Full list of updates: version 1.20 updates

Full code changelog: https://github.com/StephaneCouturier/Katalog/compare/v1.19...v1.20

Download Katalog: https://sourceforge.net/projects/katalogg