Functional image file upload

[ca2longoria]

Summary

Here's the part that killed the charasprite project (short life regardless). Time for an input-file element to push data to Spritely, and for Spritely to receive.

Honestly, at this point, I've had to do a fair amount of investigation into the multipart/file-data format, such that it might have been less work to do said research and write the request body data parser, myself, rather than relying on nanohttpd's SimpleWebServer class.

Redoing in NanoHTTPD, itself.

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Concrete Requirements

• [x] - override NanoHTTPD's prior-deprecated serve method.
• [x] - NanoHTTPD receives multipart/file-data data
• [x] - data to BufferedImage

[ca2longoria]

SimpleWebServer seems to override NanoHTTPD's mulipart/form-data functionality, which is awful and makes no sense. Reverting usage to NanoHTTPD, and building our own simple server from there. Hopefully, it'll handle regular files just fine, already, and this won't involve too much labor.