Fix output to named tuple member retrieval

This allows to properly initialise and use database views that uses python keywords as output name.

This will require an update to the replay found in https://gitlab.idiap.ch/beat/beat.examples/ to properly map the class output to the cls object member.

Fixes #16 (closed)

beat/backend/python/test/prefix/databases/integers_db/1.json

@@ -12,7 +12,8 @@
                     "outputs": {
                         "a": "user/single_integer/1",
                         "b": "user/single_integer/1",
-                        "sum": "user/single_integer/1"
+                        "sum": "user/single_integer/1",
+                        "class": "user/single_integer/1"
                     }
                 }
             ]
@@ -29,7 +30,8 @@
                         "a": "user/single_integer/1",
                         "b": "user/single_integer/1",
                         "c": "user/single_integer/1",
-                        "sum": "user/single_integer/1"
+                        "sum": "user/single_integer/1",
+                        "class": "user/single_integer/1"
                     }
                 }
             ]
@@ -45,7 +47,8 @@
                     "outputs": {
                         "a": "user/single_integer/1",
                         "b": "user/single_integer/1",
-                        "sum": "user/single_integer/1"
+                        "sum": "user/single_integer/1",
+                        "class": "user/single_integer/1"
                     }
                 },
                 {
@@ -56,7 +59,8 @@
                         "a": "user/single_integer/1",
                         "b": "user/single_integer/1",
                         "c": "user/single_integer/1",
-                        "sum": "user/single_integer/1"
+                        "sum": "user/single_integer/1",
+                        "class": "user/single_integer/1"
                     }
                 }
             ]