removed more deprecation warnings, convert error found

Ok this should all be fine except for one error that crops up:
ERROR: `convert` has no method matching convert(::Type{QueuedWorkerTask}, ::PriorityQueue{QueuedWorkerTask,Float64})
This is due to line 155 of timholy's commit be8ac90, so I reverted to the original for that one line

Sorry for so many commits in this PR (6-7 I think), but I was distracted all day yesterday while trying to get this up to date.  My plate is full so I haven't yet asked the question why the assignment on 155 ends up generating the error, I only note here that it does.