Put old "non-unit-tests" in the attic instead

Lately, I have been troubled [*] by the `tests/not-unit` directory. Originally, this directory was created when the CTest framework was introduced -- this was then everything in the `tests/` directory which was not easily transferred into a unit test, hence the name.

However, it seems that this can be confusing; people expects everything under `tests/` to be... well tests, although not *unit* tests, and this is actually a reasonable explanation. 

Not being automated, they have no real value as tests, however. And they are not really examples of anything either. It would be nice to see if they compiled from time to time, but having them in the build gave me problems when I started to integrate patches into dune-cornerpoint.

Then it struck me: The attic. Things that are in the attic are things which we don't use actively anymore, but which we still don't have the conscience to rid ourself of. We may go in there once in a while to check things, but we don't expect it to work flawlessly anymore.

Thus, this is the revival into the build system from Marcus (see opm/dune-cornerpoint#36) but rebased into the opm-core tree and with everything moved to an `attic/` directory.

[*] I loose sleep easily, see the punchcard.