More robust add torrent file
More robust add torrent file

MIME-type can be many different strings so instead just assume data is
base64 and split.

Fixes case with "data:application/octet-stream;base64,..."
YodaDaCoda/chrome-transmission-remote-plus,zsorizs/chrome-transmission-remote-plus,zsorizs/chrome-transmission-remote-plus,YodaDaCoda/chrome-transmission-remote-plus,zsorizs/chrome-transmission-remote-plus