Add REST API for instance group api extension

Support the Creation, Read, Delete, and List of server groups.

Refactored the code to use objects (https://review.openstack.org/#/c/38979/
Renamed from "instance group" to "server group".

Implements: blueprint instance-group-api-extension

Change-Id: I650a8f191dea5eab5b4b1828f0b9f65e33edea2a

doc/api_samples/os-server-groups/server-groups-get-resp.json

@@ -0,0 +1,9 @@
+{
+    "server_group": {
+        "id": "5bbcc3c4-1da2-4437-a48a-66f15b1b13f9",
+        "name": "test",
+        "policies": ["test_policy"],
+        "members": [],
+        "metadata": {}
+    }
+}

doc/api_samples/os-server-groups/server-groups-get-resp.xml

@@ -0,0 +1,8 @@
+<?xml version='1.0' encoding='UTF-8'?>
+<server_group xmlns:atom="http://www.w3.org/2005/Atom" xmlns="http://docs.openstack.org/compute/api/v1.1" id="5bbcc3c4-1da2-4437-a48a-66f15b1b13f9" name="test">
+  <policies>
+  <policy>test_policy</policy>
+  </policies>
+  <members/>
+  <metadata/>
+</server_group>

doc/api_samples/os-server-groups/server-groups-list-resp.json

@@ -0,0 +1,11 @@
+{
+    "server_groups": [
+        {
+            "id": "616fb98f-46ca-475e-917e-2563e5a8cd19",
+            "name": "test",
+            "policies": ["test_policy"],
+            "members": [],
+            "metadata": {}
+        }
+    ]
+}

doc/api_samples/os-server-groups/server-groups-list-resp.xml

@@ -0,0 +1,10 @@
+<?xml version='1.0' encoding='UTF-8'?>
+<server_groups  xmlns:atom="http://www.w3.org/2005/Atom" xmlns="http://docs.openstack.org/compute/api/v1.1">
+  <server_group id="5bbcc3c4-1da2-4437-a48a-66f15b1b13f9" name="test">
+  <policies>
+  <policy>test_policy</policy>
+  </policies>
+  <members/>
+  <metadata/>
+</server_group>
+</server_groups>

doc/api_samples/os-server-groups/server-groups-post-req.json

@@ -0,0 +1,6 @@
+{
+    "server_group": {
+        "name": "test",
+        "policies": ["test_policy"]
+    }
+}

doc/api_samples/os-server-groups/server-groups-post-req.xml

@@ -0,0 +1,5 @@
+<server_group name="test">
+  <policies>
+  <policy>test_policy</policy>
+  </policies>
+</server_group>

doc/api_samples/os-server-groups/server-groups-post-resp.json

@@ -0,0 +1,9 @@
+{
+    "server_group": {
+        "id": "5bbcc3c4-1da2-4437-a48a-66f15b1b13f9",
+        "name": "test",
+        "policies": ["test_policy"],
+        "members": [],
+        "metadata": {}
+    }
+}

doc/api_samples/os-server-groups/server-groups-post-resp.xml

@@ -0,0 +1,8 @@
+<?xml version='1.0' encoding='UTF-8'?>
+<server_group xmlns:atom="http://www.w3.org/2005/Atom" xmlns="http://docs.openstack.org/compute/api/v1.1" id="5bbcc3c4-1da2-4437-a48a-66f15b1b13f9" name="test">
+  <policies>
+  <policy>test_policy</policy>
+  </policies>
+  <members/>
+  <metadata/>
+</server_group>