add default values required to make it possible to terminate keywords early

for many of them the RM says "default is undefined" but that I've come
to the conclusion that this doesn't mean that no default could be
applied, but that the simulator is allowed to screw up if the values
of them are accessed. (Note that in this sense this change is no
change from the current situation, but makes the screw-up more
explicit.)

In particular, note the GRIDUNIT keyword which had some serious JSON
syntax errors in it but so far the unit tests worked anyway for some
reason...
make items which do not have a default un-defaultable

this was a much more common problem than it seemed initially...
make the parsing stage pass even if non-defaultable items have been defaulted

... but throw later when trying to access the data of the item in
question.

Note that this was demanded by [at] joakim-hove and that I do not want
to be held responsible for any issues which are caused by this
approach. (read: please direct your barks to Joakim if you fell on
your nose because of this...)
Revert "add default values required to make it possible to terminate keywords early"

This is not necessary anymore with approach of the previous commit...
Merge pull request #355 from andlaus/no_default_default

Remove "default" default values
Added EQUALREG json configuration
Added maskedSet() and initMask() GridProperties<T>
Added const to GridProperty::containsNan()
Added GridProperty::getDimensionString()
Added method GridProperties::getInitializedKeyword()

The getKeyword() method will autocreate and initialize a keyword if you
ask for one which is supported, but has not yet been accessed. The new
getInitializedkeyword() method will raise an exception if the keyword
has not already been initialized.
Added support for EQUALREG in EclipseState
Added test for EQUAL.
Added GridProperty::maskedMultiply() method
Added MULTIREG keyword.
Added support for MULTIREG keyword in EclipseState
Added GridProperty::maskedAdd() and maskedCopy()
Added ADDREG keyword
Added support for ADDREG keyword
Added COPYREG keyword
Added support for COPYREG keyword