Merge branch 'changelog-facets-all-all-comm' into 'master'

Changelog Added entry about All_All communication on facets.

See merge request !185 (merged)

(cherry picked from commit 985cc2db)

0a228e29 Changelog Added entry about All_All communication on facets.

CHANGELOG.md

 # dune-uggrid 2.8 (unreleased)
 
+* Added support for All_All communication on facets.
 * Removes support for `_2` and `_3` macros.
 * Remove support for XDR.