add opm-core to the ewoms prerequisites
remove the dune-istl from the list of opm-material prerequisites

the only reason dune-istl was required was that the spline class used
ISTL's tridiagonal matrix. Since the spline class moved into the core
(along with a more capable tridiagonal matrix), ISTL is no longer
required by opm-material.
Findewoms.cmake: fix typo

it's 'start.hh', not 'start.h'...
Catch up to opm-material reorganisation.

Specifically, file <opm/material/constants.hh> was renamed to
<opm/material/Constants.hpp> and this renaming must be reflected in
the CMake probes for opm-material.
Use dSYM bundles as debugging containers (on MacOS X)

gdb on MacOS X does not seem to be very fond of "flat" dSYM files, but
it can read the bundle variant fine. Thus we change that to enable
debugging across several tools.
Enable MPI if path is given

Assume that ./configure --with-mpi= also implies --enable-mpi; if you
absolutely want to specify path without enabling (?!) then you can do
--with-mpi=... --disable-mpi (in that order).

This patch look for anything after the equal sign of the --with
parameter and only set the variable _MPI_PREFIX_PATH if that is given;
it always toggle USE_MPI.
Pass BUILDNAME and SITE options along to CTest/CDash

By passing these options through ./configure, one can use dunecontrol
to build a complete stack and still get a customized description in
CDash (such as when building in a cluster or VM where the actual machine
name does not matter, or when you want to add key options to the name
shown) without having to run a second configuration just to set those
in the cache.

Also fixes a bug where --with-cmake would skip any further option
specified after it.
Allow static linking for SuiteSparse to be forced

If -DSUITESPARSE_USE_STATIC=ON, then the build system will only look for
static versions of the libraries that are part of SuiteSparse, even if
dynamic/shared versions are present on the system. Thus, the default of
preferring dynamic libraries can be overridden.

SuiteSparse is rarely built ourselves, but still uncommon enough to not
be present on computing clusters.

This patch allows us to install the libraries on a workstation, for
instance from package suitesparse-devel and link to it statically
without having to maintain our own build tree.
Merge branch 'cmake_03'