EclipseWriter: attempt to fix the well summary output for activeWells != totalWells

The summary files now always features all wells which ever appear in
the deck in every timestep (even if they are not specified for the
time step). This _should_ fix the crashes when writing Eclipse output
in the Norne deck, but I have no idea if the resulting summary file is
correct. More testing would be thus highly appreciated...
Merge pull request #625 from andlaus/fix_wells_in_summary_output

EclipseWriter: attempt to fix the well summary output for activeWells != totalWells
Remove unnecessary grid from fluid test.
Make all construction from deck use EclipseGrid.

The deck constructor is still present, but it will construct an
EclipseGrid object instead of doing its own equivalent processing.
Add PINCH support to grid construction.
Create pointer-to-const objects.

Older gcc (4.4) does not allow conversion of shared_ptr<Foo> to
shared_ptr<const Foo>. Pointed out by @bska.
Use new constructor for EclipseGrid.
Merge pull request #633 from atgeirr/use-pinch

Unify grid construction, allow PINCH