Replace membership page with summary of current project organisation

[pgleeson]

This is a bit out of date: https://docs.openworm.org/Community/membership/

A replacement page or pages should discuss:

• OpenWorm Foundation
• Senior Contributors
  • Process for becoming one
• OpenWorm Board
  • Point to http://openworm.org/people.html for current members
  • Overview of board processes (elections, officers, monthly meetings)
  • AGM - frequency and past minutes