Version 0.12

Fixes a few issues:

• Filenames can be duplicated (e.g. same filename, two folders)
• Filenames can now have multiple periods, but please don't do this for the sanity of any other software you use.
• You can now remove a labels forward from the current image - this is quite useful for tracking if you mess up and accidentally miss something.
• Solves a subtle bug where zero area bounding boxes would be generated and cause crashes.