improve and update server configuration documentation (rebased from develop)

Makes a start on the work for https://trello.com/c/Gpwp1WkC/188-improve-server-config-docs and removes some information about both OMEIS archeology and, from https://trello.com/c/avvIvqCk/67-5-0-3-follow-up, our long-neglected OpenGL clients.
--rebased-from #948
To parellel the comments made for the server, I think this listcould benefit from being duplicated into a separate "minimum client specification" list, and the recommended versions increased to security supported versions, i.e. MacOS 10.8, Windows Vista/7.