handing of specific endian.LITTLE when needed

[herbi3]

• Added endian.LITTLE dict for registers that require wordorder to be endian.LITTLE now both BIG & LITTLE work at the same time

• additional registers export_control_mode, export_control_limit_mode, export_control_site_limit, storage_control_mode, storage_ac_charge_policy, storage_ac_charge_limit, storage_backup_reserved_setting, storage_default_mode, rc_cmd_timeout, rc_cmd_mode, rc_charge_limit, rc_discharge_limit

• Removed third battery support. seems to conflict with battery1 and battery3 always shows as connected (even when there is no third battery)