Make raspberry pi raspbian file system read-only

Based on https://hallard.me/raspberry-pi-read-only/

• setup.sh - Tested OK on 2017-11-29-raspbian-stretch*.img
• Old version named setup.sh.jessie - Tested OK on 2017-04-10-raspbian-jessie*.img

TODO:

• Check if https://github.com/MarkDurbin104/rPi-ReadOnly has anything I'm missing.
• Watchdog

Tricks for certain apps:

• Apache2, edit logpath in /etc/apache2/env
• Chromium-browser, use --user-data-dir /tmp/something
• Lightdm - fixed via setup.sh
• Rpi-Cam-Web-Interface: mount /var/www/html/media/ on tmpfs or external rw disk

Usage after setup:

• If you need to change anything, run rw to remount file system read/write. Then ro to make it read only.
• Logs can be read with the command readlog and readlog -f.