Intention is to test flash driver along with BLE radio.
Added flash shell module with commands for erase, write-check, read and
co-operation with radio stress test.
Signed-off-by: Carles Cufi <carles.cufi@nordicsemi.no>
Signed-off-by: Andrzej Puzdrowski <andrzej.puzdrowski@nordicsemi.no>