EclipseState: make specifying anything which requires a grid an error if no grid could be instantiated

this is the second version of the patch which is based on top of the current master, so that it is possible to create some grid properties if only the `DIMENS` keyword is present in the `RUNSPEC` section. in addition to that, this patch enables `EclipseState` creation even if `DIMENS` is not in the deck. Basically this should make Joakim as well as me happy...