dataproxy/Community.js: abstract the prefixing of the communities payload URL

app.js

@@ -31,6 +31,7 @@
 var wwt = {
   gitShortSha: '<%= gitinfo.local.branch.current.shortSHA %>',
   staticAssetsPrefix: '<%= profile_data.webclient_static_assets_url_prefix %>',
+  communitiesUrlPrefix: '<%= profile_data.communities_url_prefix %>',
 
   app: angular.module('wwtApp', [
     'mgcrea.ngStrap',

dataproxy/Community.js

@@ -58,7 +58,7 @@
 	  }
 	  root = wwt.wc.createFolder();
 
-	  root.loadFromUrl('//worldwidetelescope.org/Resource/Service/Payload', function () {
+	  root.loadFromUrl(wwt.communitiesUrlPrefix + '/Resource/Service/Payload', function () {
 	    deferred.resolve(root.get_children());
 	  });
 	}

profile-dev.yml

@@ -6,5 +6,6 @@
 
 webclient_static_assets_url_prefix: ''
 userweb_url_prefix: https://beta.worldwidetelescope.org
+communities_url_prefix: https://beta.worldwidetelescope.org
 webgl_engine_url_prefix: https://beta.worldwidetelescope.org/engine/latest  # no CDN to avoid staleness issues
 maybe_min: ''

profile-prod.yml

@@ -13,6 +13,12 @@ webclient_static_assets_url_prefix: https://beta-cdn.worldwidetelescope.org/webc
 # served from /webclient/ and they're in the root, so:
 userweb_url_prefix: ..
 
+# A prefix to prepend to paths for links to the WWT Communities, which will look
+# like "/Resource" before prefixing. On the production server, the Communities
+# and "user website" are both in the same place, but in testing we might split
+# them out.
+communities_url_prefix: ..
+
 # The URL prefix for finding the Web engine. In production, we want to route
 # this through the CDN. In development we want to use the testing version or
 # perhaps even a local hacked version.