cmake: add openMP support

this is slightly hacky, but the OpenMP support that was included in
the build system did not work properly without hacks in the cmake
modules which wanted to use OpenMP
implement support for thread parallel linearization using OpenMP

thanks to the context objects concept this was relatively easy. Note
that this requires you to use an OpenMP compatible compiler, i.e. any
supported GCC version will do, but the current CLang (3.4) won't.
fix output of tensorial VTK fields in the MPI-parallel case

this implies a few new reference solutions...
fix compilation with old versions of GCC

these require a copy constructor for objects to be usable with
std::vector even if the constructor is not actually called. Since this
constructor was explicitly deleted, so the build failed.

This patch is very specific for GCC, but since the issue does not
appear with more modern versions of it and also not with clang, I do
not want to bother to write a build system test for this. Also, we
provide a copy constructor for GCCs up to 4.6, but I could not test it
on GCC 4.5 and 4.6, so the fix may not be necessary for them. (but
this does not really matter since all development should be based on
more modern compilers anyway...)
fix FvBaseLocalJacobian's GCC 4.4 copy constructor

for some reason, this resulted in a segmentation fault in some cases...
some smallish parallel ctest improvements

the goal is to make it faster on computers with many cores: The
easiest way to do this is to ensure that the longest running tests are
not taking too much time and that they need about the same time. Thus
this patch contains the following changes which limits the CPU time
taken by each test to about two minutes in debug mode on my machine:

 - the water-air problem using the non-isothermal primary variable
   switching model now uses an 16x16 instead of a 32x32 grid. as a
   compensation it now runs for a year instead of 5000 seconds and the
   global grid refinement is now tested.
 - the end time of the lens problem ctests is now 3000 instead of
   30000 seconds. The binary itself does not change at all.
 - sort the tests in the CMakeLists.txt roughly in the order of their
   required time. (this will cause ctest not having to wait for long
   running test which were started late for too long.)
NCP model: throw an exception if the minum activity coefficient is <= 0

most likely this will be produces by a negative pressure. If this
happens it is probably better to immediately abort the time
integration anyway...
TPFA: change the way how gradients are calculated

before this, gradients had the direction of the face between two
finite volumes, now they exhibit the direction of the two
FV-centers.

For axis-aligned grids the result is identical for interior faces, but
it is different for boundary faces or if faces are not
axis-aligned. This patch fixes the SPE9 troubles with anisotropic
permeabilities on tilted grids...
change the gravity correction code

this had some problems if the gravity was not aligned to the face
(i.e., gravity being either in the face's plane or perpendicular to
it).

with this SPE9 seems to run completely with an unmodified grid,
although there are still some issues with the wells...
adapt the the table related API changes of opm-parser
Merge pull request #7 from andlaus/table_improvements

adapt the the table related API changes of opm-parser
powerinjection problem: make it work for 2D and 3D grids

and some minor variable renames in the base gradient calculator so
that a delta won't be mistaken for a derivative...
resetTerminal(): only use documented ANSI escape codes

the ones which where send to the TTY before this commit were taken
from the 'tset' utility and I could not find documentation for some of
them. Some of these caused trouble with 'screen' under some
circumstances, probably because they were invalid or unsupported..
set CMake policies CMP0026 and CMP0048 to OLD

this is required for CMake 3.0 to stop it complaining that we access
the LOCATION target property and set the *_VERSION_* variables ourselves.
cmake: policies must be protected by if()

... unless they shall break older cmake versions which don't know
about them. this seems to be a bit superfluous to me, but whatever...