Bug#636783: TC chair appointment

[Ian Jackson <ijackson@chiark.greenend.org.uk>]

I mentioned this on IRC but forgot to get it into the agenda:

The TC chair arrangements have what is arguably a bug, which is that
the TC cannot change a sitting chair other than by the chair resigning
or leaving the committee.

I think the TC chair should be reappointed regularly (annually?), and
that a new chair election should be held when the TC composition
changes.

If we are having a formal TC member retirement scheme, and TC chair
election when a new member is appointed, then perhaps making explicit
provision for time-based chair retirement is unnecessary.

Ian.