switches: add ground disconnectors, read normal open attribute (#1915)
switches: add ground disconnectors, read normal open attribute (#1915)

Signed-off-by: Luma <e69bc83fa9c8497733c18bc5c38bed4741f6e183@aia.es>
powsybl/powsybl-core,powsybl/powsybl-core,powsybl/powsybl-core