Add an option to save the raw unextracted cache files when using --download

[wertercatt]

I'd like to use runescape-cache-tools in order to download a complete cache so that I don't have to use the launcher to do it.

[villermen]

Hey. Sorry for the slow response, I've been pretty busy lately.

Writing cache files is something that I'd really like to add. I believe I have already done some work for it a year or so ago. It's still going to take a lot of work, and I don't know when I will get around to it. It'll be there eventually, but don't get your hopes up too soon =(