WIP How to document your extension

This book isn't published yet, but I want to get this page up
and running. Will uncomment when CiviVolunteer books is up.

remove hookref-old.md and move all content into relevant files. Add wordpress setup information for hooks.

Commit for issue #104

Added a requirement for community and official ext

Fix typo in hook_civicrm_angularModules.md

Update hooks page

- update overview
- add tips and warnings
- add section on hook naming
- replace long code blocks (that focus more on other components) with simpler blocks that show hook usage only
- replace validate with validateForm
 - remove complicated example for setting custom values
 - update tokenValues function to match newer version
 - remove examples of executing raw SQL

Update documentation.md

I found that I needed this package locally or I got this error: `ImportError: Failed loading extension 'pymdownx.superfences' from 'pymdownx.superfences', 'markdown.extensions.pymdownx.superfences' or 'mdx_pymdownx.superfences'` when trying to build

hook_civicrm_apiWrappers: More tweaks

This commit mostly adds Markdown tweaks.

I also struck the comparison to pre/post hooks... because I enjoy removing words. 

hopefully improve the docs on API_Wrappers

typo in method-name

for non civicrm links class=no-popup is needed

related to https://issues.civicrm.org/jira/browse/CRM-20187

added angular

Styleguide To Do

@nganivet and I worked out this wording, based on a discussion in the Extensions Working Group. The aim is to help eliminate surprises and increase trust.