Tidy the core alumni list.

• Fix some recent missorting. The text on the website claims that this list is in reverse chronological order. Choose the newest "end date" for individuals with multiple ranges as the date to sort against since this seems to be the one used most commonly.
• Within a group of developers who stepped down at the same time (e.g. election handover), sort by last name then first (this was the most common pattern I could see in the existing entries).
• Remove a duplicate entry for myself.