Added test for DG basis classes.

Only 2d so far.
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.
added: license
Merge pull request #124 from akva2/add_license

Add COPYING file with license
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
Bring ParameterGroup interface into scope.

The constructor accepts a parameter::ParameterGroup reference and thus
needs a valid interface in scope.  Relying on header pollution is
unwise.
Fix DisjointColumn test case

The test started failing in commit 7d7f62e, but this was not detected
due to no automatic test environment.  The commit changed the cell
numbering from "per-column (K,I,J)-ordering" to "per-plane
(I,J,K)-ordering".  Consequently, the "correct_answer" seized to be
correct.

This change restores the "correct_answer" in the ordering introduced by
commit 7d7f62e.

While here, adjust style of the DisjointColumn test case for legibility.
Merge pull request #134 from bska/release-cleanup

Assorted clean-ups in preparation of release