Updates changelogs for 2.1.6
Merge remote-tracking branch 'origin/2.1-maint'

Conflicts:
	community/kernel/CHANGES.txt
	community/server/CHANGES.txt
Remove duplicate properties during store migration from 2.1 to 2.2

Signed-off-by: Jakub Wieczorek <jakub@jakub.cc>
More complicated test data for the duplicate property removal on store migration
Further progress on simplifying the duplicate property fix-up in 2.1-2.2 migration