This almost 100% backwards compatible. The only difference being that
in the rc options/get output CacheMode will be output as strings
instead of integers. This is a lot more convenient for the user. They
still accept integer inputs though so the fallout from this should be
minimal.
Before this change options were read and set in native format. This
means for example nanoseconds for durations or an integer for
enumerated types, which isn't very convenient for humans.
This change enables these types to be set with a string with the
syntax as used in the command line instead, so `"10s"` rather than
`10000000000` or `"DEBUG"` rather than `8` for log level.