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

- 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

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

extension lifecycle - add formal review process

content from:
https://docs.google.com/document/d/1nUfSqIpMQplrj6cv4Nvkxf-dR3NClghhKdB_Xw3MpYY/edit
No substantive content changes, but quite a bit of content clean up
during import

Fixing link for User Guide :: English :: latest

Added Limitations section

since these list items are all also headings and thus will appear in the
TOC nav on the right side of the page

Closes #90

clarify form/bao role

Fixes #79

per comments from @eileen here https://github.com/civicrm/api4/issues/14#issuecomment-278860730