FIX: Return 401 for bad authentication scheme

https://github.com/embedthis/appweb-4/issues/254
DOC: Clarify httpWriteBlock [255]

https://github.com/embedthis/appweb-4/issues/255
FIX: Update conn->lastActivity in readEvent [issue 256]

Added update of conn->last activity in readEvent.

https://github.com/embedthis/appweb-4/issues/256