Updates to Chapter 7 - Common Problems & Solutions

- Shortened section titles and added subheaders 'Problem' and
  'Solution' sections (except second section, for which the
  problem being addressed was unclear).

- Reworded first section (View Nesting); minor rewording and
  corrections elsewhere.

- Switched order of sections regarding rendering parent from child
  and triggering updates in other views.

- Added 'validate: true' flag to the call to set in the ValidateAll
  example (0.9.10 change).