Added test for DG basis classes.

Only 2d so far.
Opm::WellState::init(): Handle shut wells

This is a minor bugfix to account for the presence of shut wells
(characterised by "ctrls[w]->current < 0").  The existing code would
lead to indexing outside the "ctrls" array in the context of a shut
well.
Merge remote-tracking branch 'upstream/master'
Merge pull request #117 from bska/master

Release preparation: Fix out-of-bounds indexing in context of shut wells
Merge remote-tracking branch 'upstream/master' into dg-improvements
Refactored limiter functions.

The two limiter functions were very similar, and were unified in a single
method, with a bool argument to choose method variety.
Added functionAverage() method to DGBasis classes.
Use functionAverage() instead of direct coefficient access.

This fixes the issue with limiters on multilinear basis.
Add methods totalFlux() and minCornerVal().

Also started refactoring applyMinUpwindLimiter() using the
added methods.
Prepare for processing two-dim. grid

Allow a two-dimensional grid to be sent to compute_geometry() without
the assertion triggering. Route three-dimensional grids to the existing
implementation.
Compute properties for edges in 2D
Compute properties for cells in 2D
Set size properties in grid when allocating structure

There is little chance that the client want to set them otherwise since
that would make the structure inconsistent, and having all the clients
do the work is just needless duplicate labour.
added: license
Merge pull request #124 from akva2/add_license

Add COPYING file with license
Unit test the geometry computations for 2D grids
Refactored applyMinUpwindLimiter().
Added evalFunc() method.

This public method is not virtual, and implemented in the base class using calls to
the virtual methods. Not yet used by the DG solver.
Merge remote-tracking branch 'upstream/master' into dg-improvements
Merge pull request #120 from atgeirr/dg-improvements

Further DG time-of-flight improvements