Improve admin documentation

[intelliant01]

In relation to https://github.com/RechercheTech/mss/issues/20 and otherwise (May be start a tips and tricks section (based on common queries encountered) -

• [x] Replace references to thin-client and fat-client
• [ ] Introduce a section wherein the boot menu is explained.
• [x] How to seek remote support - connect using wifi, epoptes, etc.
• [x] Epoptes launcher creation for a teacher
• [x] Mass user addition
• [ ] Mass user deletion

[geets04]

What are the final keywords need to be replace for thin-client and fat-client