standalone: implement User fields when_last_accessed and when_updated

[artfulrobot]

When last accessed tracks when the logged in user last made a PHP request to the site, limited to one update per minute.

When updated tracks when a user record was updated.

[civibot]

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[artfulrobot]

Mentioning people who may be interested @wmortada @jaapjansma

[jaapjansma]

Looks good to me. I am not sure why the test is failing.

[artfulrobot]

Merging thanks for review.