markdown rules - specifying that internal hyperlinks should use absolute paths with preceding slashes

EXT-21: Migrated/updated documentation around extension publication and automated distribution

1) This seems like a site admin task, not a developer task. If you're reading this page, I assume you
   already know how to do this. I'd argue this belongs in the user guide (if it's not already there).
2) It doesn't seem right to me that one should configure their extensions directory before
   deciding whether or not to write an extension. First check the extensions directory to
   see if someone has already built the thing. If not, only then does make sense to start
   playing with your environment config.
3) If we keep it in the developer guide, I'd put it at the beginning of the instructions
   for creating a module extension (https://wiki.civicrm.org/confluence/display/CRMDOC/Create+a+Module+Extension).
   These are currently undergoing migration from the wiki to mkdocs, so I'm blocked from making such
   an update at this time.

Nice!

 * Cleanup syntax of `define()`s. Add another.
 * Add `angularDebug=1` / `crm-ui-debug`.
 * Add more ways to clear the cache.
 * Consolidate discussions of xdebug (for all other/undocumented/external)

Migrate wiki page: Debugging

Wiki import "Before you start" and "Recommendations" pages

Style Guide

inforporate content from civicrm.org/developer-resources into "community" page

Conflicts:
	mkdocs.yml

api/usage.md - The OO example doesn't work. Fix it.

Conflicts:
	redirects/wiki-crmdoc.txt

https://wiki.civicrm.org/confluence/display/CRMDOC/Debugging+for+developers

new page: Prerequisite skills