seems like some compilers don't overwrite an inline method of a
template class with its specialization. A compiler warning would have
been nice to have in this case, though...
this makes it possible to define more complicated initializers for
grid properties. (needed for example for keywords like ISGU.) This
patch does not introduce them yet, but only adds the necessary
infrastructure.
notes:
- to get around cyclic definitions in template classes, the
EclipseState is changed to a (defaulted) template parameter which
causes the compiler to only look up the class definition at
instantiation time.
- using std::shared_ptr in the property initializers would lead to
cyclic references which would cause memory leaks. To avoid that,
plain old references where used in most places. I think this is
okay as the GridProperty objects should be considered internal to
EclipseState and thus the EclipseState object should live at least
as long as GridProperty objects...
e.g. Eclipse specifies that for PERMX only the topmost layer needs to
be specified, i.e. the following is valid on a 3x3x3 grid
```
PERMX
9*10 /
```
the previous behaviour was to throw.
also, mark if data items have been defaulted, i.e., the item of
```
PERMX
* /
```
will now return true for 'defaultApplied()'.
it returns a const reference to a vector which does not allow
manipulation of its members. the getData() can thus be safely called
on constant GridProperty objects.
this uses a small amount of template magic, to automatically change
the API of the GridProperty class depending on wheter it is
instantiated for double or for int.
