Updated API for compatibility with latest rocksdb.

Removed following properties of ColumnFamilyOptions, which have been deprecated for some time. (They cause issues with Cython right now, and will be obsolete in v7 anyway.)

* `soft_rate_limit`
* `hard_rate_limit`
* `rate_limit_delay_max_milliseconds`
* `purge_redundant_kvs_while_flush`
* `skip_log_error_on_recovery`