C2MS12 — Rework 8.12 Product Messages Intro

Section 8.12 Product Messages is the only major section of that Chapter without an Intro. The intro should discuss the purpose and use of all product messages. See any other major section of chapter 8 for examples.

Additionally, none of the Product Messages contain a Message Summary Table (see Table 8-146 Command Echo Message Summary).

All the other messages except Navigation Data Messages have summary tables. These NDMs are represented somewhat differently in C2MS, so not too worrisome that they don't, but Product Message are clear outliers with the other message types.

These tables typically are followed with examples, also missing for Product Messages.