Content overview page: make Author column sortable by default on new installations

Given the extent of my issue update in #27 and the fact that it was over seven years ago, this issue probably isn't a good novice contribution candidate. Thanks!

Rolled into an MR.

I think the decision on whether this makes sense is valid when sites implement hook_user_format_name_alter, however those sites could simply turn it off?

I don't think we need tests here as we're just toggling on sorting - this should be tested elsewhere.

I don't think we need profiling here as the db query is simple.

Seems pretty straight forward.