Fixed expansion of "plugins"

Closes #26

There was no need to add @list, and it was causing JSON-LD to expand the
URI of 'plugins'

senpy/schemas/context.jsonld

@@ -37,9 +37,6 @@
       "@type": "@id",
       "@container": "@set"
     },
-    "plugins": {
-      "@container": "@list"
-    },
     "options": {
       "@container": "@set"
     },

senpy/schemas/plugins.json

@@ -10,8 +10,6 @@
           "items": {
             "$ref": "plugin.json"
           }
-        },
-        "@type": {
         }
       }
     }

tests/test_models.py

@@ -109,13 +109,15 @@ class ModelsTest(TestCase):
                                 }
                             }})
         c = p.jsonld()
-        assert "info" not in c
-        assert "repo" not in c
-        assert "extra_params" in c
-        logging.debug("Framed:")
+        assert '@type' in c
+        assert c['@type'] == 'plugin'
+        assert 'info' not in c
+        assert 'repo' not in c
+        assert 'extra_params' in c
+        logging.debug('Framed:')
         logging.debug(c)
         p.validate()
-        assert "es" in c['extra_params']['none']['options']
+        assert 'es' in c['extra_params']['none']['options']
         assert isinstance(c['extra_params']['none']['options'], list)
 
     def test_str(self):
@@ -158,6 +160,13 @@ class ModelsTest(TestCase):
         g = rdflib.Graph().parse(data=t, format='turtle')
         assert len(g) == len(triples)
 
+    def test_plugin_list(self):
+        """The plugin list should be of type \"plugins\""""
+        plugs = Plugins()
+        c = plugs.jsonld()
+        assert '@type' in c
+        assert c['@type'] == 'plugins'
+
     def test_single_plugin(self):
         """A response with a single plugin should still return a list"""
         plugs = Plugins()