Simplify setting of flag that indicates shared object

Instead of having the name of the module set for each flag, use the
available standard option. Mixing shared objects and static libraries
in the same build is not a very realistic scenario anyway.

This enables us to call configure without actually having a particular
module; the script may then be used on a group level.
Merge pull request #12 from rolk/012_configure

Update CMake scripts to commit f6d44238 from opm-core