Improve admin documentation

[intelliant01]

In relation to RechercheTech/mss#20 and otherwise (May be start a tips and tricks section (based on common queries encountered) -

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

[geets04]

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