Add “forgot password” functionality to login

[Mr0grog]

The functionality exists over in the API, but we should put a UI for it—or at least a link to the API page—here so people can find it.

[Mr0grog]

(Prompted by someone forgetting their password and being unable to figure out how to reset)

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed in seven days if no further activity occurs. If it should not be closed, please comment! Thank you for your contributions.

[Mr0grog]

Still important.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed in seven days if no further activity occurs. If it should not be closed, please comment! Thank you for your contributions.

[lightandluck]

Added never-stale label