since we still support g++-7, where filesystem is marked experimental,
we introduce a wrapper header and expose the namespace to use
as Opm::filesystem.
for gcc we unconditionally link with libstdc++fs in the python bindings.
the setup.py stuff links as c code, not c++ code, so it is not
automatically added on any gcc version. this might prove unportable
later.
Every header is self-contained and includes only what it must to
function, relying on users include what they need in source files,
adopting a pay-what-you-use model (in particular for internal
dependencies).
With this commit the generation of built in keywords is completely
changed. The most important changes include:
1) We have autogenerated a class for each keyword in the new
ParserKeywords { ... } namespace.
2) The autogenerated classes derive from ParserKeyword, and the
default constructor will build of a fully initialized
ParserKeyword instance, i.e. the keyword used to parse the EQUIL
keyword can be instantiated as simple as:
ParserKeywords::EQUIL kw;
3) The generated keywords have built in static constants for keyword
and item names, and item default values. That way it should be
possible for the compiler to catch trivial errors like trying to
access the keyword "PoRO"; also the the access to default values
means that properties can be initialized without actually
insantiating a DeckKeyword.
4) Two new classes Generator/KeywordLoader and
Generator/KeywordGenerator have been created, with the help of
these classes the keyword generation code is significantly
simplified.
