README: Update and consistency fixes

- Sorted "3.0) Supported Games" in alphabetic order and moved the none specific game parts to the bottom of that chapter
- Sorted "5.0) Running ScummVM" in alphatic order and adapted all references

- Added "Discworld II notes" to "3.0) Supported Games"
- Added "Nippon Safes Inc. Amiga notes" to "3.0) Supported Games"
- Added "Zork games notes" to "3.0) Supported Games"
- Added "Datafiles" to "3.0) Supported Games"

- Added "AmigaOS4" in "9.0) Compling"
- Added "Amiga/Macintosh" to "3.14) The Feeble Files notes"
- Added lots of missing subchapters to the main chapter list in "7.0) Music and Sound)"

- Changed "Maniac Mansion" title to better reflect the contents