Added default values for keywords ENPTVD/ENKRVD

Setting defaulted parameters to -1 for later identification.
The ParserKeyword->parse() method will throw if the raw input argument is not finished.

Requires several changes to assure that the rawkeyword instances are
marked as finished before reacing the ParserKeyword->parse method.
Added boolan flag scalar = true to DeckItem.

The purpose of this flag is to keep track of whether a keyword is
supposed to have only one element, i.e. scalar, or several. The
defaultApplied method only makes sense in the case of scalar items, this
method will now throw if it is called on a non-scalar item.
Verified behaviour of defaults (i.e. *) for multivalued items.