[manual] Complete Part I

[tajmone]

Port and polish chs. 5-6 an apps. A-D of Part I:

• Ch. 5. Using a ToolMaker Based System
• Ch. 6. Common Definitions
• App. A. The PL/O Example
• App. B. Error Messages
• App. C. Syntax Notation
• App. D. References

Rename part1-*.adoc source docs adopting a two-digit counter for better ASCIIbetical file sorting.