ssa_db_helper.[h c]: API for SSA DB load/save functionality

Signed-off-by: Ilya Nelkenbaum <ilyan@mellanox.com>
Signed-off-by: Hal Rosenstock <hal@mellanox.com>
ssa_db_helper.[h c]: Cosmetic formatting changes

Signed-off-by: Hal Rosenstock <hal@mellanox.com>