this is meant for those nasty keywords where the dimension of an entry
depends on a user-defined value of some field of a (potentially
different) keyword. One example for this are the surface rates of the
produced fluids for the .CON(INJ|PROD).* keywords which exhibit
different units depending on whether the user choses to control for
the surface gas or the liquid rate.
the approach taken in this patch is to convert all numbers to NaN if
the unit is queried in SI (via item->getSIDouble()). It might be more
desireable to throw an exception in this case, but this approach would
be more elaborate and NaNs should be quickly noticeable by the users
of this code.
I tried to adapt all implemented keywords, but it's quite likely that
I missed some...
the motivation for this is the 'TSTEP' eclipse keyword.
the reason why this dimension is not simply called 'Time' is that in
eclipse, different keywords might use different units, e.g. one
keyword could use seconds, another could use years while a third uses
days. As an added bonus, the used time units may be different for
different scales but identical in others (e.g., for one keyword times
might be specified in 'days' for the metric as well as for the
labscale, but in 'days' and 'hours' for another second keyword.)
