Akin to config.h, we write project-version.h whenever the VCS sha hash
of the project changes. This file can then be included to embed this
into the project. Since this changes more frequently, we choose another
file than config.h. Care is also taken to not rewrite the header if the
information doesn't change, but the project is rebuilt.
It is only used in one place, where it can easily be replaced by its
expansion. The reason for removing it is that it depends on the name
of the project, and I intend to read this using a routine it the very
directory it is including, hence the need for a different approach.
Developers that are working to familiarize themselves with OPM will
probably start out in CMakeLists.txt to figure out where the project
declare its dependencies, thus the list should be referred to from
there instead of inside one of the sub-modules.
The hooks are meant to be project specific, and should therefore
either know their own name or at least have access to a variable with
that name in it.
