Typo in S5_1.py and KLC docs

I'm almost embarassed to report this, but there is a typo in S5_1.py. One error message says "footprint existence is not going to be checked if --footprint is not specified", but the parameter is actually named "--footprints".

But while I'm here, I'd like to suggest an improvement to this docs paragraph:

https://klc.kicad.org/#_klc_helper_scripts

At first, I assumed I have to run the scripts from KiCad's Command Prompt and of course I was getting errors. It took me a while to realize I need to use "normal" Python and regular system console. It would be nice if you added a line that makes that clear.