Added some useful information to image upload resp

* Refactored the controller. Placed all the upload logic inside a new service
* Changed the tests to make it happen
* Changed the default field name of image to "file". Previously was "image"
* Added some useful (and elcodi related) response data in the upload response
    * resize route wildcarded
    * view route wildcarded
I don't really like to add a `status` field to the response, there's the HTTP status for this, so returning a 200 is an OK.
But I see this is scattered all over the project, so I better open an issue to address that.