- Removed caches for entity numbers since they are not needed if optimizations are turned on when compiling.
- Added delete_cell_range() function to delete a whole consecutive cell chunk at once and re-compute face
adjacencies afterwards. Major speed boost if large cell chunks have to be deleted.

git-svn-id: http://www.openvolumemesh.org/svnrepo/OpenVolumeMesh/trunk@194 66977474-1d4b-4f09-8fe9-267525286df2