I'd prefer to pass it for consistency reasons (because basically every
other class which takes an EclipseState object also requires a deck
object), but some people seem to have a very strong option about
this...
or more accurately: "use FIELD or METRIC units", LAB and PVT-M units
are still unsupported, but they seem to be pretty exotic and are also
not supported by opm-parser either...
note that this patch requires an API change (with the usual
consequences for all downstream modules which use this class) because
the deck needs to be passed to EclipseWriter. If somebody knows a
canonical way to get the names of the written units from EclipseState,
this is API change is not required.
