Added macros for product name (#3455)

Allows products that rebrand Che to easily reuse Che docs and have their own product name substituted for Che's

docs/_config.yml

@@ -26,6 +26,10 @@ name: Eclipse Che Docs
 description: Cloud workspaces for development teams
 url: https://www.eclipse.org/che/
 
+product_name: "CHE"
+product_mini_name:  "Che"
+product_formal_name: "Eclipse Che"
+
 twitter:
   username: eclipse_che
 
@@ -103,4 +107,4 @@ defaults:
     scope:
       path: "_docs/artik-ide-plugin"
     values:
-      categories: [ "artik" ]
+      categories: [ "artik" ]