Feature/friend

Friend authentication for http basic api calls and form based for those going via the website and ajax.
why not put all the doseq processing in a separate fn, which makes the need to return the response map clearer.

```
  (if (sensor-exists? session device_id type) 
        (do
          (validate-and-insert-measurements measuurements)                                                                                                                  
          {:response {:status 202 :body "Accepted"}})                                                                                                                                                            
        {:response {:status 400 :body "Provide valid device_id and type."}}))
```