Introduce members

Created by: IanMayo

Signed-off-by: Ian Mayo ian@planetmayo.com

Preview here: https://deploy-preview-5--eclipsefdn-science.netlify.com/membership/

Note, three flaws:

• iSencia no longer appears to have a Eclipse membership number. ID 1167 is appears to no longer be valid. Well, iSencia seems to have been incorporated in a larger parent organisation.
• The participation levels are sorted in alphabetical order, which puts "Participating Members" before "Steering Committee Members". I can't find a software fix to this, I guess renaming one group to control the order is the only workaround I can think of.
• The "All members" button doesn't work. Issue reported here