Platform 254

@Wikia/platform-team 

First phase of refactoring environment variables (more to come)

1) set up /etc/environment in chef and use those environment variables in PHP
2) use constants instead of strings for environment vars
3) create minimal LocalSettings.php to remove dependency on deploy tools or chef 
4) removed some "getEnvironment()" helper functions and use global vars directly

Next phase: there is another set of helper functions checking URL's in order to figure out if they are in the preview/verify environment.  I am contacting the authors to make sure their use cases are covered.  

Next phase after that: refactor how Slots are done (we only need 1 slot right now so this is low priority).

@wladekb  Please review the bucky changes, in particular the change from "development" to "dev" and "production" to "prod".  I assume that won't break anything, but it may require some other change to support it?
Where are the `WIKIA_DC_*` constants defined?