[Documentation] Fix link to core modules and only list real dependencies, not all of the core modules
[Tests] Don't rely on DGF to initialize YaspGrid in testlargedomainnumbers
[MultiDomainMCMGMapper] Use GlobalGeometryTypeIndex and an array to store offsets

The mapper in dune-grid has recently been converted to store the
per-GeometryType offsets in a std::vector indexed by the
GlobalGeometryTypeIndex, which improves lookup times by replacing an
expensive map lookup with a simple array access.

This patch does the same thing for the MultiDomainMCMGMapper and also
gets rid of the separate size variable - that information has been moved
to the end of the offsets array, where it is automatically built as part
of a call to std::partial_sum, converting per-GeometryType sizes to
offsets.

Thanks to Christoph Grüninger for bringing this up!
[MultiDomainMCMGMapper] Fix broken implementation of contains() with a codimension template parameter
Merge branch 'releases/2.3'

Pull in a couple of important fixes from release branch

* releases/2.3:
  [MultiDomainMCMGMapper] Fix broken implementation of contains() with a codimension template parameter
  [MultiDomainMCMGMapper] Use GlobalGeometryTypeIndex and an array to store offsets
  [Tests] Don't rely on DGF to initialize YaspGrid in testlargedomainnumbers
  [Documentation] Fix link to core modules and only list real dependencies, not all of the core modules

Conflicts:
	README.md