Test GeometryGrid with a DiscreteCoordFunction

This case was not tested before. Besides the actual testing it is useful to document the precise meaning of the DiscreteCoordFunction interface.

mentioned in issue #69 (closed)

mentioned in issue infrastructure/releases#1

changed milestone to %DUNE 2.6.0

added 91 commits

• 9ca8095d...56b86683 - 89 commits from branch master
• dafe9441 - [yaspgrid] implement method subIndex for entities of all codimensions
• 2192866b - Test GeometryGrid with a DiscreteCoordFunction

Compare with previous version

I rebased this one to master and implemented the YaspGrid's subIndex method for all codimensions in !227 (merged).

added 2 commits

• c276b928 - [yaspgrid] implement method subIndex for entities of all codimensions
• c21a981c - Test GeometryGrid with a DiscreteCoordFunction

Compare with previous version

mentioned in commit d31f1532

merged