improved handling of failed tape uploads to score server

When initially mass-uploading personal tapes, a single failed upload
caused the whole process to be restarted from scratch, ignoring all
tapes that were already uploaded. This improvement marks completely
uploaded tape directories to be able to skip them after failures and
repeated upload attempts. (In addition, non-existing tape directories
are skipped right away, without checking for each single tape file.)

Another improvement remembers if tapes were not uploaded (either
because the score server was disabled, or because uploading the tape
failed). If this happens, the game adds an entry to upload tapes to
the setup menu, and asks for uploading missing tapes on next start.