image_compress and image_uncompress refactor

[sebo-b]

First of all - thank you for your great work with reverse engineering Fossil Hybrid. It is really impressive!

I was going to add a better command line parameters support but ended up with quite a significant refactor of these two tools.

What's improved:

• command parameters are now documented (--help)
• more errors are detected now
• width and height are optional (are read from the file)
• format is optional (default rle)
• added uncompression of raw files

I think it is properly tested as I have generated multiple (around 100) random PNG files (b&w, color, alpha, no alpha, square or not), and all generated raw and rle files are exactly the same as with the original tool.