Release 0.9.1

v0.9.1

Accidentally removed chapter 3.3 other models in v0.9.0, add back.

Release 0.9.0

Delta with 1.0.0-draft6:

1. update version to 0.9.0, following ratification policy.
2. re-organize the chapters.
3. update register ERR_REQINFO.ip to ERR_REQINFO.v
4. other updates based on feedbacks