Add script to locally serve MkDocs site through docker

This way the docker image shows the repository that was used to generate
the image and people can go to that repo to look at the Dockerfile used.

Correct default permission for custom API entities; clarify example. Fix #136

CRM-19813 - Document support for hooks via Symfony

This updates the docs to ensure that hook parameters exactly match the names
in the code.

Prior to 4.7.19, the names of hook-parameters didn't really matter (as long
as they were in the right order).  In 4.7.19, the names took on extra
significance because Symfony-based listeners use objects and fields (e.g.
`$event->firstParam`) instead of ordered params (`function($firstParam)`).

 * Rewrite "Events"
 * Use more consistent style in the two examples
 * Move some "notes" into new section, "Methods"

What's wrong with a little inversion of logic?

Update API schedule option description - 4.3 plus

Updated line 627 to "For use with CiviCRM 4.3 and later," per info from @totten

Update documentation on documentation

Added Chris Burgess' and Sean Madsen's contributions from StackExchan…

Closes #130: Clarity around "overrides" language.

Update pr-review.md

Add links to other documentation, clean up grammar and formatting, clarify a couple points

Remove invalid (outdated?) requirement that extensions provide documentation.

WIP PR Review

fix broken link to blog post

Update extend-stages.md