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
CornerpointChopper::writeGrdecl(): Write fewer items per line

This is in preparation of increasing the vector output precision to
reduce the impact of rounding errors in subsequent upscaling.  The
change impacts floating-point vectors only.

Background: The ECL simulator stipulates an upper bound on the
number of characters in a record (i.e., one line) and while we don't
have such limits, there's no reason to emit lines that can't be
input by other tools.
CornerpointChopper::writeGrdecl(): Increase vector precision

This commit increases the precision of the (floating-point) vector
output (e.g., permeabilities) from method writeGrdecl().  This
reduces the impact of rounding errors when the sub-set sample is
output to disk for subsequent processing (e.g., property upscaling).