Use semantic markup (#645)

* Use semantic markup.

* Linting.

* Define docsite targets.

* Forgot one env var.

* Add array stubs.

plugins/modules/docker_prune.py

@@ -124,14 +124,14 @@ RETURN = '''
 containers:
     description:
       - List of IDs of deleted containers.
-    returned: I(containers) is C(true)
+    returned: O(containers=true)
     type: list
     elements: str
     sample: []
 containers_space_reclaimed:
     description:
       - Amount of reclaimed disk space from container pruning in bytes.
-    returned: I(containers) is C(true)
+    returned: O(containers=true)
     type: int
     sample: 0
 
@@ -139,14 +139,14 @@ containers_space_reclaimed:
 images:
     description:
       - List of IDs of deleted images.
-    returned: I(images) is C(true)
+    returned: O(images=true)
     type: list
     elements: str
     sample: []
 images_space_reclaimed:
     description:
       - Amount of reclaimed disk space from image pruning in bytes.
-    returned: I(images) is C(true)
+    returned: O(images=true)
     type: int
     sample: 0
 
@@ -154,7 +154,7 @@ images_space_reclaimed:
 networks:
     description:
       - List of IDs of deleted networks.
-    returned: I(networks) is C(true)
+    returned: O(networks=true)
     type: list
     elements: str
     sample: []
@@ -163,14 +163,14 @@ networks:
 volumes:
     description:
       - List of IDs of deleted volumes.
-    returned: I(volumes) is C(true)
+    returned: O(volumes=true)
     type: list
     elements: str
     sample: []
 volumes_space_reclaimed:
     description:
       - Amount of reclaimed disk space from volumes pruning in bytes.
-    returned: I(volumes) is C(true)
+    returned: O(volumes=true)
     type: int
     sample: 0
 
@@ -178,7 +178,7 @@ volumes_space_reclaimed:
 builder_cache_space_reclaimed:
     description:
       - Amount of reclaimed disk space from builder cache pruning in bytes.
-    returned: I(builder_cache) is C(true)
+    returned: O(builder_cache=true)
     type: int
     sample: 0
 '''