Update account access expire emails to point to new Renew button on Account page

[jonasbardino]

With the introduction of the simple Renew access button on the Account page we would prefer users to rely on that whenever possible to avoid the full sign up form and the several ways it can be used to create incompatible renewal requests (changed fields, passwords, etc.).

The expire warn email should therefore be updated to list it as the primary option and clean up some of the old methods except as a last resort e.g. when account access already expired.

[jonasbardino]

Optionally also add inline web page warnings about upcoming access expiry with link to renew, or even better implement auto renew for ext accounts where Peers already allow it.

[jonasbardino]

Resolved with #242 . Added follow-up tag for the optional longer-term improvements.

[jonasbardino]

Doh, this change requires the per-user Account page to be available, which is not currently the case on gdp sites like SIF. The question now is whether we should make the effort to integrate that as e.g. a tab or allowed hidden page on such sites right away or if we should make a temporary conditional in the notification code to point to some legacy renew link for that case (@Martin-Rehr ?) .

[Martin-Rehr]

Doh, this change requires the per-user Account page to be available, which is not currently the case on gdp sites like SIF. The question now is whether we should make the effort to integrate that as e.g. a tab or allowed hidden page on such sites right away or if we should make a temporary conditional in the notification code to point to some legacy renew link for that case (@Martin-Rehr ?) .

Let's expose the "per-user Account page" through a tab Account on the GDP admin frontpage.