PropagateUpload: Better messaging for 507 #5537

PropagateUpload: Better messaging for 507 #5537

It now produces a summary error message indicating the problem.

Adjust blacklist database table to contain 'errorCategory'. This is
useful for two things:
  - Reestablishing summary messages based on blacklisted errors. For
    example if we don't retry a 507ed file, we still want to show the
    message about space on the server
  - Selectively wiping the blacklist: When we have ui for something like
    "I deleted some files, please retry all files now!", we want to
    delete all blacklist entries of a specific category only.