Options with numbers for RocksDB are all casted as float64.

[cv711]

Any particular reason for this one?

Users usually don't expect setting the log level like this "info_log_level" : 3.0, and if you use an int casting it fails and the option is never set

[mschoch]

The code is ancient and dates back to a time when there was a misunderstanding about how JSON parsing worked in Go.