chore(util-fns): minor cleanup and refactoring (#1562)

This only impacts language dependent variable and path definitions:
- Removed deprecated variable.
- Hoisted useful variable definitions from quickstart into _util-fns.
- Minor fix in regexp of path translation function

public/_includes/_util-fns.jade

@@ -23,13 +23,18 @@
 //- TS arrays vs. Dart lists
 - var _Array = 'Array';
 - var _array = 'array';
-//- Deprecate now that we have the articles _a and _an
-- var _an_array = 'an array';
 
 //- Promise vs. Future, etc
 - var _Promise = 'Promise';
+- var _PromiseUrl = 'https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise';
+- var _PromiseLinked = '<a href="' + _PromiseUrl + '">' + _Promise + '</a>';
 - var _Observable = 'Observable';
 
+//- Directories & folders
+- var _appDir = 'app';
+- var _indexHtmlDir = 'project root';
+- var _mainDir = _appDir;
+
 //- Location of sample code
 - var _liveLink = 'live link';
 

public/docs/dart/latest/_util-fns.jade

@@ -5,16 +5,20 @@ include ../../../_includes/_util-fns
 - var _decorator = 'annotation';
 - var _Array = 'List';
 - var _array = 'list';
-- var _an_array = 'a list'; //- Deprecate now that we have the articles
 - var _a = 'an';
 - var _an = 'a';
 - var _priv = '_';
 - var _Lang = 'Dart';
 - var _Promise = 'Future';
+- var _FutureUrl = 'https://api.dartlang.org/dart_async/Future.html';
+- var _PromiseLinked = '<a href="' + _FutureUrl + '">' + _Promise + '</a>';
 - var _Observable = 'Stream';
 - var _liveLink = 'sample repo';
 - var _truthy = 'true';
 - var _falsey = 'false';
+- var _appDir = 'lib';
+- var _indexHtmlDir = 'web';
+- var _mainDir = 'web';
 
 mixin liveExampleLink(linkText, exampleUrlPartName)
   - var text = linkText || 'live example';
@@ -36,7 +40,7 @@ mixin liveExampleLink2(linkText, exampleUrlPartName)
 -   // if(extn == 'dart') return path;
 -   var baseName = getBaseFileName(path) || path; // TODO: have getBaseFileName() return path
 -   var baseNameNoExt = baseName.substr(0,baseName.length - (extn.length + 1));
--   var inWebFolder = baseNameNoExt.match(/^(main|index(\.\d)?)$/);
+-   var inWebFolder = baseNameNoExt.match(/^(main|index)(\.\d)?$/);
 -   // Adjust the folder path, e.g., ts -> dart
 -   folder = folder.replace(/(^|\/)ts($|\/)/, '$1dart$2').replace(/(^|\/)app($|\/)/, inWebFolder ? '$1web$2' : '$1lib$2');
 -   // Special case not handled above: e.g., index.html -> web/index.html

public/docs/dart/latest/quickstart.jade

@@ -6,8 +6,6 @@ block includes
   - var _prereq = 'the Dart SDK'
   - var _angular_browser_uri = 'package:angular2/platform/browser.dart'
   - var _angular_core_uri = 'package:angular2/core.dart'
-  - var _appDir = 'lib'
-  - var _indexHtmlDir = 'web'
 
 block setup-tooling
   :marked

public/docs/ts/latest/guide/component-styles.jade

@@ -31,7 +31,7 @@ p Run the #[+liveExampleLink2()] of the code shown in this chapter.
   specifying any selectors, rules, and media queries that we need.
 
   One way to do this is to set the `styles` property in the component metadata.
-  The `styles` property takes #{_an_array} of strings that contain CSS code.
+  The `styles` property takes #{_an} #{_array} of strings that contain CSS code.
   Usually we give it one string as in this example:
   
 +makeExample('component-styles/ts/app/hero-app.component.ts')(format='.')

public/docs/ts/latest/quickstart.jade

@@ -4,8 +4,6 @@ block includes
   - var _prereq = 'Node.js'
   - var _angular_browser_uri = '@angular/platform-browser-dynamic'
   - var _angular_core_uri = '@angular/core'
-  - var _appDir = 'app'
-  - var _indexHtmlDir = 'project root'
 
 :marked
   Our QuickStart goal is to build and run a super-simple