[Arm-dev] Updates to basic server howto - Webmin added and stuff

I have updated the basic howto:

http://www.htt-consult.com/Centos7-armv7.html

Webmin is easy to install, but seems a bit slow on the Cubie. Perhaps that is simply due to first time accesses, and what Webmin builds on first access to a function.

Webmin is now defaulting to a TLS connection and builds a default cert. You may want to replace that with one more customed to your preferences.

Chronyd caveats now reflect best practices for customizing a systemd service.

Remaining known changes for this is switching to using nmcli for the interface config. I am close....

Would be nice to figure out what the problem with the SSD and SELinux is so, if needed, I can add in info on that...

Now to tackle the SELinux mail problems...