make sure images set over the API are displayed

At the moment the popit front end doesn't follow the same data model as
popolo for images so when you include and image URL over the API they
aren't displayed by the website. This does the required processing on
the uploads to fix that.

Fixes #432

src/app.js

@@ -243,7 +243,13 @@ function popitApiApp(options) {
   });
 
   app.post('/:collection', validateBody, function (req, res, next) {
-    req.collection.create(req.body, function (err, doc) {
+    var body = req.body;
+    // if there's an image and no body.images then add one as the popit front end uses
+    // that at the moment
+    if ( body.image && !body.images ) {
+      body.images = [ { url: body.image } ];
+    }
+    req.collection.create(body, function (err, doc) {
       if (err) {
         return next(err);
       }
@@ -275,6 +281,7 @@ function popitApiApp(options) {
         doc = new req.collection();
       }
       delete body.__v;
+
       /* this is to make sure that the _id property is the same for things added via
        * the api and the front end. If not then elasticsearch doesn't index it as it
        * confuses it's auto mapping.
@@ -289,6 +296,12 @@ function popitApiApp(options) {
         });
         body.images = images;
       }
+
+      // if there's an image and no body.images then add one as the popit front end uses
+      // that at the moment
+      if ( body.image && !body.images ) {
+        body.images = [ { url: body.image } ];
+      }
       doc.set(body);
       doc.save(function(err) {
         if (err) {