Set taxonomy terms to have revisions by default

[rosiel]

Discussed at the MIG, we would like to take advantage of the new ability for taxonomy terms to have revisions and make all vocabularies make revisions by default.

This is a blanket move that seems most in line with the desire for an audit-able repository.

To clarify, this does not turn on revisions. An editor can, regardless of the setting for the vocabulary, choose to create a revision. This setting just checks that checkbox by default. An editor can still, since we don't have content moderation installed, uncheck the box and make a change without creating a revision.