"Request a review" instead of "request a request".

(files still need to be moved around)

https://wiki.civicrm.org/confluence/display/CRMDOC/Database+Reference

Corrected the incorrectly used word 'thought' to 'through'. 
Corrected grammar of 'how to write an extensions'. 
Clarified the meaning of 'ensuring that you really need to start coding'.
Added full stops to 'aka' abbreviation to make it clearer it is an abbreviation.
Changed 'developer environment' to more conventional and accurate phrase 'development environment'.

style guide - calling the "User Guide" the "User Guide" instead of the "User and Administrator Guide"

* documenting custom header IDs
* removing rule about using one H1 element (that's in style guide now)
* clarifying thad admonitions only work when enabled

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

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.

 * 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)