Clarify default cache type per edition
Merge pull request #3098 from cleishm/default_cache

[2.0] Clarify default cache type per edition
Merge remote-tracking branch 'upstream/2.0-maint' into 2.1-maint
Merge remote-tracking branch 'upstream/2.1-maint'

Conflicts:
	community/kernel/src/docs/ops/cache.asciidoc