OpmInit.cmake is one of the first includes and most importantly before
the opm-*-prereqs.cmake files are include. The macro is needed to make
the policies set in all CMakefiles. OpmSetPolicies should be called in
the toplevel CMakeLists.txt file.
This fixes a lot of warnings experienced in downstream modules that
got triggered by the opm-*-prereqs.cmake files. At some calls the
policies were at other not.
On the other hand new warnings about soon to be deprecated policies
CMP0026 and CMP0048 appear at least for cmake version 3.13.4.
But that should be fixed in another PR.
use pure config mode.
we no longer compile a test application for the libraries,
however checks have been tightened by making sure version of
all opm modules are the same.
this allows for putting prereqs directly in the module repositories
