Change default folder to open in 'Load' dialogue boxes

[leandervaneekelen]

Currently, whenever you open a loading dialogue box, e.g. when you open a mask in the 'Overlays' tab or an XML annotation file in the 'Annotations' tab, the default folder that is opened seems to be the folder where the currently open WSI is located. ASAP seems to remember this folder when you exit the program.

It would be convenient if ASAP also remembers the folder where the currently open XML annotation/TIF mask is and show that in the dialogue box. This prevents unnecessary browsing of folders if the WSI and the XML/mask are located in different folders.