Doing dev on a channel that doesn't use content facet, but taxonomy
facets instead, and keep getting reminded this field isn't actually
compulsory. So figured rather than unticking it every time I reinstall I
should make a PR :)

…tional

Make facets on a channel optional, as is documented from #281.

…ctories into 3.x

…ition

Re-run core update for our blocks added after the fact.

(a) the new 're-use existing field' form doesn't suffer the JS switch of
  form that create field does. So the entity types don't appear on that
  form when they still do for create.
(b) the new form settings field has a toggle for enabling a default
  value.

This reverts commit 7ca5237.

Feature/3.x/geo entity