Bugfix datahandle contains for specialization of codim 0.

Closes #41

See merge request extensions/dune-alugrid!40

GatherScatterBaseImpl< codim=0 >.

ALUGridCube.

-DALUGRID_DISABLE_METIS=FALSE is specified.

[bugfix] remove spurious include to rpc/rpc.h

See merge request extensions/dune-alugrid!38

of the library to all headers (cmake problem). For all other downstream
modules the grid selection is still written to config.h

HAVE_DUNE_HASH was hardwired to 1 in the 2.4 release and is gone since 2.5.
As dune-alugrid is no longer compatible with the 2.3 release, we can safely
remove this guard.

As decided on the developer meeting, dune-corepy has been renamed to
dune-python. This patch add support for both flavors of the module. We
do not verify whether both modules are installed.

impl/binaryio: use standard std::streampos

See merge request extensions/dune-alugrid!37

std::istream:streampos is non-standard and fails when building with clang.

improved the runtime configuration check for the python package

See merge request !36

CMakeLists.txt file

make it possible to not pass dimgrid to grid constructor.

See merge request !34

fix an issue with python_install in case pip was not found

See merge request !35