Allow downloads from arbitrary URLS

If the download task contains a 'url', instruct the device to download
from that URL instead of genieacs-fs.

lib/tasks.coffee

@@ -322,6 +322,18 @@ this.download = (task, methodResponse, callback) ->
     return
 
   if methodResponse.type isnt 'DownloadResponse'
+    if task.url?
+        methodRequest = {
+          type : 'Download',
+          fileType : task.fileType or '1 Firmware Upgrade Image',
+          url : task.url,
+          username: task.username,
+          password: task.password,
+          successUrl : task.successUrl,
+          failureUrl : task.failureUrl
+        }
+        callback(null, STATUS_OK, methodRequest)
+    else
       db.filesCollection.findOne({_id : mongodb.ObjectID(String(task.file))}, (err, file) ->
         if not file?
           callback('File not found')