cntl.h header confusing or ambigious

Trying to set the poll interval via a connstr, I found this in cntl.h

https://github.com/couchbase/libcouchbase/blob/master/include/libcouchbase/cntl.h#L992-L993

It seems to refer to

https://github.com/couchbase/libcouchbase/blob/master/include/libcouchbase/cntl.h#L83

But then in discussion it turns out that when supplied at the connstr (the most common case) it is handled in seconds.  

The cntl.h docs need to be cleaned up.