[general] Convert the "guest" manual into the "general" manual

[heysokam]

Reasoning:

1. Consensus seems to be that guests won't be explicitly looking for a manual.
2. On the other hand, creators+developers+hosts all need general-purpose information that is currently buried in multiple sections.

This issue solves both problems by:

• Removing the guests section of the manual
• Creating a general section in the manual
• Storing all of those general purpose concepts and articles inside the new section.

[heysokam]

Completed with #89