API Microversioning

This patch set adds API microversion support along
with the first API microversion: start/end time for
CONTINUOUS audits.

APIImpact

Implements: blueprint api-microversioning
Depends-On: I6bb838d777b2c7aa799a70485980e5dc87838456
Change-Id: I17309d80b637f02bc5e6d33294472e02add88f86

api-ref/source/samples/audit-create-request-continuous.json

@@ -8,5 +8,7 @@
         ]
     },
     "audit_type": "CONTINUOUS",
-    "interval": "*/2 * * * *"
-}
+    "interval": "*/2 * * * *",
+    "start_time":"2018-04-02 20:30:00",
+    "end_time": "2018-04-04 20:30:00"
+}