message: [gui] intro: enable pruning by default unless disk is big
  Color the text "GB needed for full chain" orange for nodes that barely have enough space.
diff: @@ -274,6 +274,11 @@ void Intro::setStatus(int status, const QString &message, quint64 bytesAvailable
  {
  freeString += " " + tr("(of %n GB needed)", "", requiredSpace);
  ui->freeSpace->setStyleSheet("QLabel { color: #800000 }");
  + ui->prune->setChecked(true);
  + } else if (bytesAvailable / GB_BYTES - requiredSpace < 10) {
  + freeString += " " + tr("(%n GB needed for full chain)", "", requiredSpace);
  + ui->freeSpace->setStyleSheet("QLabel { color: #999900 }");
  + ui->prune->setChecked(true);
  } else {
  ui->freeSpace->setStyleSheet("");
  }
  