GroupTree::prinTree() takes std::ostream argument
Removed debug output clutter
Default: Updates to ParserItem::equal()

 1. The boolean flag m_defaultSet() is included in the actual
    comparison.

 2. The compare functions is implemented as a functions template.
Default: Implemented ParserxxxItem::scan() with template
Default: Changed defaultApplied bool to enum

We now have an enum which can keep track of three possible states for
the data in a deck item:

  VALID   : A valid value has been set
  DEFAULT : The default value has been applied
  NOT_SET : The value has not been set.

The intention is to throw if/when a DeckItem with status == NOT_SET is
accessed.
Default: Changed default handling in ParserItem

This is the first of several large commits changing several aspects of
the handling of defaults. The overall main purpose of these changes is
to protect against using non sensible values in the case the values have
not been sensibly specified in the deck. The changes in this commit
include:

 1. The "default default" values to be used when an item without an
    explicit default are defaulted are removed completely.

 2. If a ParserItem is queried for a default value when no default has
    been assigned it will raise an exception.
Default: Updates to the scan routine.
Default: defaultApplied -> setInDeck()

The data values in a deck item can be in three different states, given
by the DeckValue enum in DeckItem.hpp. The three values are:

  SET_IN_DECK : The value has been set explictly in the deck.
  DEFAULT     : The value was not present in the input deck, but a default
                value has been supplied in the configuration and that value
                has been set.
  NOT_SET     : No value has been set for this item; it was not explicitly
                set in the deck and also not included in the configuration.

If you ask for DeckItem->value which is in state NOT_SET you will get an
exception. The method setInDeck() can be used to check if a value has
been set explicitly in the deck; the method defaultApplied() will check
if a default value has been applied.

Observe that the system for handling defaults is not really well suited
for multi valued data items, as it is only a scalar state variable. In
the case of multi valued data items both defaultApplied() and
setInDeck() might return true.
Default: DeckItem will throw if you ask for missing data
Default: Using setInDeck() instead of relying on size == 1
Default: Changed size_type: ALL -> SINGLE
Default: Explicitly added default == 0 for box
Default: Split options keyword to have 197 items
Default: Removed invalid default value.
Default: Changes for default applied.
Default: Explicitly set default values in config
Default: Added method hasValue()
Default: Added dataset from opm-core with test
Moved OrderMap to EclipseState/Util
Added class Value<T>

The class Value<T> will keep track of a named variable, and whether that
particular value has been explicitly initialized. Will throw
std::logic_error if trying to use an unitialized value.