Update README to better reflect current state
Update README to better reflect current state

It's - in a way - still work in progress, but a couple of things changed
since last README update.
At least some are now documented and further improvements are welcome.

volunteer-planner/volunteer_planner,pitpalme/volunteer_planner,pitpalme/volunteer_planner,volunteer-planner/volunteer_planner,christophmeissner/volunteer_planner,coders4help/volunteer_planner,pitpalme/volunteer_planner,christophmeissner/volunteer_planner,volunteer-planner/volunteer_planner,christophmeissner/volunteer_planner,volunteer-planner/volunteer_planner,christophmeissner/volunteer_planner,coders4help/volunteer_planner,coders4help/volunteer_planner,pitpalme/volunteer_planner,coders4help/volunteer_planner