Added DDL section
Added Literal vs. Expression to SQL section
Merge branch 'hotfix/871'

Close #871
Fixed formatting of class, variable names in DDL ans SQL pages
Fixed DDL imports
Fixed note section in SQL section
Merge pull request #870 from ralphschindler/feature/ddl

[WIP] Zend\Db additions
[#870] Incorporate feedback, edit

- Incorporated feedback
- Fixed tables
- Minor grammatical/flow edits
Merge branch 'hotfix/870' into develop

Forward port #870