Update authors list

development/include/people.inc:
    Move Ian to past developers list.

    Remove the link to Zoltan's website (for consistency but I suspect it's
    also deprecated).

    Add many missing people, including Matthias Güdemann who contributed
    code recently and raised the issue of copyright assignment recently.  I
    generated the list of people with "git log | grep Author".

    Sort people alphabetically by last name.

    Add a list of companies that contribute or have contributed to Mercury.
Use lowercase HTML tags.

development/include/contributions.inc:
    As above.
Minor changes to contributions page.

development/include/contributions.inc:
    As above.