Replace deprecated SDL APIs

Replace deprecated SDL SdlInstance usage with xapp-frame's SdlStorage
APIs, which have been built on top of the valid SDL SyncStorage APIs.
Upgrade xapp-frame version to v0.9.1 and SDL version to v0.8.0.
Bump routing-manager's Docker container tag to 0.7.9

Issue-Id: RIC-805

Signed-off-by: Timo Tietavainen <timo.tietavainen@nokia.com>
Change-Id: I1f7b02a1b3bcdeeeae03f8a10beb5f96a371c988
diff --git a/RELNOTES b/RELNOTES
index 28a9cb6..e9dfe1c 100644
--- a/RELNOTES
+++ b/RELNOTES
@@ -1,3 +1,6 @@
+### v0.7.9
+* Replacing deprecated SDL APIs
+
 ### v0.7.8
 * Refactoring rtmgr code