add a version.hh file
explicitly include some previously "magically included" headers

this is required since the OPM build system -- unlike DUNE's -- does
not magically include files in config.h
de-constexprify

GCC 4.4 does not know about 'constexpr' and the build system hack to
define 'constexpr' as 'const' is no longer around...
replace the custom cmake based build system by the one from OPM
Add CMake macro for test handling
make the tests work

i.e., update the CMakeLists* and tweak runtest.sh
update changelog regarding the build system change
remove the autotools based build system
use the opm-material module instead of using an internal material framework