Rename ResponseWriter 'conn' to 'rw'

Change-Id: Id0faeac080f678794c1db1601cb9c1a9ba92e926
httputil: add IsWebsocketUpgrade, fix BadRequestError inconsistency

Change-Id: I85e34fe4e87c2402fe6ab002bcd374ef0fd41141
more TODO

Change-Id: I4bdeb5d4c922b23e95c5e3789bcf65df6e0838a5
test: add World.NewPermanode

Change-Id: I737ae2f69b567eaebf13a3f7c786e06b791e2f7c