apt-key is no longer available, change  apt install script necessary

apt-key is no longer available so the install script on [https://www.pi4j.com/download/#aptppa-repository] requires change to
```
wget -qO - https://pi4j.com/pi4j.gpg | sudo gpg --dearmor -o /etc/apt/trusted.gpg.d/pi4j.gpg
echo 'deb [arch=all] https://pi4j.com/download v2 stable' | sudo tee /etc/apt/sources.list.d/pi4j.list
sudo apt update
sudo apt install pi4j
```
