PVT properties: allow them to be temperature dependent

Note that this patch does not introduce any real temperature
dependence but only changes the APIs for the viscosity and for the
density related methods. Note that I also don't like the fact that
this requires so many changes to so many files, but with the current
design of the property classes I cannot see a way to avoid this...
Merge pull request #240 from andlaus/temperature_dependent_PVT

PVT properties: allow them to be temperature dependent
Fix wrong resize() usage for Eigen::Array.
Merge pull request #246 from atgeirr/fix-test

Fix wrong resize() usage for Eigen::Array.
This commits allows for flexible choice of either ILU(0) or ILU(n) where n is a
dynamical parameter given in the parameter file. The default is 0 (as before).
In addition the relaxation parameter has been added to the parameter with the
default preserving the state from before.
Also, the default parameter for use_amg and use_bicgstab in the constructor of
CPRPrecondition have been removed.
fix parameter order for SeqILUn.
Merge pull request #252 from dr-robertk/PR/cprpreconditioner-more-flexible-choice-of-ilu

This commits allows for flexible choice of either ILU(0) or ILU(n).