Implement a fake SDL database backend

Implement a fake SDL database backend what can be used only for
local testing purposes, when SDL client does not need real DBAAS
database services. An SDL client can activate fake SDL database
backend usage when SDL instance is initiated with optional
'fake_db_backend' parameter:
  sdl_instance = SyncStorage(fake_db_backend='dict')
Value 'dict' is only supported.

Change-Id: I2ee7474175d0923617e026c306ec684b117dab60
Signed-off-by: Timo Tietavainen <timo.tietavainen@nokia.com>
diff --git a/docs/release-notes.rst b/docs/release-notes.rst
index e91338d..8951370 100644
--- a/docs/release-notes.rst
+++ b/docs/release-notes.rst
@@ -33,6 +33,11 @@
 Version history
 ---------------
 
+[2.0.1] - 2020-01-08
+
+* Add a fake database backend implementation to be used only for testing
+  purposes when the real DBAAS database service is not available.
+
 [2.0.0] - 2020-01-03
 
 * Change find_keys() and find_and_get() API functions to support glob-style