Move the building.md doc to the top of the git repo

Closes #1776

Signed-off-by: Sven Dowideit <SvenDowideit@home.org.au>

BUILDING.md

@@ -1,12 +1,3 @@
-<!--[metadata]>
-+++
-title = "Build instructions"
-description = "Explains how to build & hack on the registry"
-keywords = ["registry, on-prem, images, tags, repository, distribution, build, recipe, advanced"]
-[menu.main]
-parent="smn_recipes"
-+++
-<![end-metadata]-->
 
 # Building the registry source
 

docs/recipes/index.md

@@ -34,5 +34,4 @@ At this point, it's assumed that:
  * [using Apache as an authenticating proxy](apache.md)
  * [using Nginx as an authenticating proxy](nginx.md)
  * [running a Registry on OS X](osx-setup-guide.md)
- * [hacking the registry: build instructions](building.md)
  * [mirror the Docker Hub](mirror.md)

docs/recipes/menu.md

@@ -18,5 +18,4 @@ weight=6
  * [using Apache as an authenticating proxy](apache.md)
  * [using Nginx as an authenticating proxy](nginx.md)
  * [running a Registry on OS X](osx-setup-guide.md)
- * [hacking the registry: build instructions](building.md)
  * [mirror the Docker Hub](mirror.md)