Add 'Upload a practice map' ability

[jidanni]

On the website home page we see

Just sign up and you can start uploading and get warping!

UPLOAD MAP!

OK, we are all excited and that's what we do. Alas, on the next page it seems like we are about to contribute the map to the Library of Congress or something, more formal than a formal dinner.

OK, but gee, please add instructions how users can first upload a practice map they might have and just want to get a feel with and not something for the National Archives or whatever.