RimEclipseCase_exportProperty writes a cell property to a GRDECL style
text file and requires an explicit export file. RicfExportProperty
resolves the default file name from the command file executor's
PROPERTIES export folder and forwards to it.
The hand-written Case.export_property() wrapper is removed. The
generated Reservoir.export_property() has the same argument names and
shadows the base class wrapper anyway, so a deprecation shim would
never be reached.