Create Next/Prev File Buttons

[gcalongi]

I added a couple buttons to allow the user to skip to the next or previous detections mat if that's something you're interested in!

[DrCoffey]

This looks great! My only concern is that it doesn't check if you have saved the current detection file before loading the next one. If you had done a bunch of labeling or box adjusting and accidentally hit the button for the next file you would loose everything. I guess that is the case with the current load calls button too, so I should probably find a fix for everything. I will try to add a check to the load calls/audio buttons to see if the current calls table differs from the loaded detection file. If so it can prompt to save.