Add support for houston urls and option to download images in /api/engine/detect/cnn/lightnet/

[karenc]

• Add support for fetching houston urls in add_images

  The urls need to be prepended with houston+, for example:

  houston+http://houston:5000/api/v1/users/me

  This tells wbia to use oauth2 authentication when fetching the url.

• Allow urls in /api/engine/detect/cnn/lightnet/ image_uuid_list

  When doing POST /api/engine/detect/cnn/lightnet/, if image_uuid_list has :// it is going to download the images first before running detection.

• Support houston+ job callback urls and add callback_detailed

  OAuth2 authentication is necessary for the callback url that houston is sending so we need to support "houston+" callback urls.

  Also send all the data that you would get if you get the job results if callback_detailed is true, e.g.:

  {'status': 'completed',
  'jobid': '67bed230-01a8-464c-8421-b915e0467bca',
  'json_result': {
    'image_uuid_list': [
        {'__UUID__': '784eb312-2d7a-95a5-345c-6d0aeaa66853'},
        {'__UUID__': '51985f12-3628-4526-0545-fb47ab9a9732'}],
     'results_list': [[], []],
     'score_list': [0.0, 0.0],
     'has_assignments': False
  }
  }