Pass well list from 3D deck to the upscaling object

Extend the interface of the upscaling object so that it retrieves a
list of existing wells in the full model and provide similarily a list
of wells in the upscaled version (since the grid has changed).

Currently, there is no implementation for these methods, just the
declaration.
Create a clone of the well list to operate on

We don't want to make changes in the list submitted to us (we don't
know how *many* times it is being submitted to us, meaning we wouldn't
know if a previous instance of ourselves had already changed it, so
it is a dangerous thing to assume), so make a clone to work on.
Translate the cell indices of the well perforations

At the same time, check that the assumption that there is only one
well in each column is not being violated.
Wrapper uses well list translated to top surface

Wells are translated from the full grid to the top surface grid. The
state is kept the same, because it is the same number of wells, they
are just located in a "different" place (squashed to 2D).
Merge pull request #22 from rolk/022_wells

Translate well list from fine grid to top surface (squash to 2D)