Revamp 2016

[danielballan]

• New "event-based architecture" lead-in, co-written with @tacaswell
• New main page linking to project docs
• Summary diagram on main page (TODO)
• Link to some accidentally orphaned pages; delete others.

[danielballan]

already pushed -- as usual, this is an improvement on what was there, even in its WIP state http://nsls-ii.github.io/index.html