Use /assets for client assets

- Route `/assets` -> `build/public`, falling back on `public`
- Moved destinations for `nodebb.min.js`, `acp.min.js`, `admin.css`, `stylesheet.css`, `templates`, and `sounds` to `build/public`
- r.js modules previously routed through express are now symlinked into `public/build/src/modules`
- minfiles no longer served from a memory cache
- use config `views_dir` setting everywhere template directory is used
- fix cache buster `v=v=`

public/src/ajaxify.js

@@ -338,7 +338,7 @@ $(document).ready(function () {
 			callback(templates.cache[template]);
 		} else {
 			$.ajax({
-				url: RELATIVE_PATH + '/templates/' + template + '.tpl' + (config['cache-buster'] ? '?v=' + config['cache-buster'] : ''),
+				url: config.relative_path + '/assets/templates/' + template + '.tpl' + '?' + config['cache-buster'],
 				type: 'GET',
 				success: function (data) {
 					callback(data.toString());