Governance directory page for pg.o

As discussed during the PGConf.dev developer meeting, here is a first
pass attempt at a patch for pg.o to add a "Governance Directory" page,
along with a few supporting new pages. Specifically it proposes to move
the "Committers" and "Sysadmin" pages off the wiki and onto pg.o, and
adds pages for the Contributors Committee and Recognized Contributors
Policy (as discussed back in February at FOSDEM).

There is more that can and should be done here, but I was hoping to get
this set of changes in place before trying to boil the ocean.
* More/missing teams/committees
* Add "how to volunteer/help" to individual team pages
* Other stuff?

Comments/thoughts/flames?

--
Joe Conway
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com