Integrate RNIB with SDL SyncStorage to xapp-frame

Integrate RNIB with SDL SyncStorage to xapp-frame

SdlInstance type with its API functions has been deprecated and its
source code will be removed at some point of time from sdlgo repository.
sdlgo repository provides the SyncStorage type what should be used
instead of the SdlInstance type.

Upgrade xapp-frame to use Nodeb-rnib reader version 1.2.1, which has
a new reader type, which takes SyncStorage type reference in.

Change xapp-frame RNIB writer instance rNibWriterInstance to use SDL
instance of type SyncStorage.

Issue-Id: RIC-805

Signed-off-by: Timo Tietavainen <timo.tietavainen@nokia.com>
Change-Id: I4d6010c806370f0157a94f6f79f04ff90e11b63b