add PVCDO keyword and fix typo pvdco -> pvcdo

this is used in opm-core but I doubt that these code paths have
actually been tested recently because the parser would have thrown up
as soon as it had encountered PVCDO...
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.
Merge pull request #179 from andlaus/add_pvcdo_keyword

add PVCDO keyword and fix typo pvdco -> pvcdo
Merge pull request #178 from joakim-hove/data-with-default

Data with default
Fixed typo Pvdco -> Pvcdo in installed headers
New keywords ENDNUM; IMBNUM and SATNUM.
Comment out unused function argument.
Rename local variable to avoid shadowing.
Commented out unused function arguments.
Renamed local variable to avoid shadowing.
Renamed function arguments to avoid shadowing.
Merge pull request #187 from osae/new-kw

New keywords ENDNUM; IMBNUM and SATNUM.
Merge pull request #182 from atgeirr/warning-suppresssion

Warning suppresssion