Add CMake backwards compatibility for version < 2.8.3

Add features that aren't available in early versions of the 2.8.x
release series, enabling use of 2.8.0 if needed (e.g. Ubuntu 10.04)
Merge pull request #261 from rolk/261_parse

Sideport of OPM/opm-material@48f6d4d to opm-core
Merge branch 'master' into devel