Extend voip app to allow override which modules load per user config like apps.

Just need array list of voip modules to load in users voip app config. Example from user's db doc:
...
   "apps": {
       "voip": {
           "id": "voip",
           "label": "Hosted PBX",
           "icon": "device",
           "desc": "Manage vmboxes, callflows ...",
           "api_url": "http://kazoo.example.com:8000/v1",
           "default": false,
           "modules": [ "account", "bulk", "media", "device", "callflow", "conference", "groups", "user", "phone", "vmbox", "menu", "registration", "resource", "featurecode", "cdr", "queue", "directory" ]
       },
   .....
},
...