FlexLM install

A little while ago, I saw this post on FlexLM licensing: https://lnkd.in/euQBFuWh.

I have been in the same position with _many_ CAD/EDA tools, so I wrote this: https://lnkd.in/euD8rZZg guide. I'm installing alterad and saltd in the example but it should be useful for anyone trying to get FlexLM working - which is most EDA/CAD tools that I come across.