intermediate changes to do better when scrolling pipeline list view
issue #581, issue #464 pipeline list controls are custom - solves multiple UI shortcomings, hopefully w/o introducing too many new ones
Final touches to pipeline list UI for Mac
Merge branch 'plvui' into multiprocessing
Removed print statements from pipelinelistview
Added sockopt LINGER = 0 to all sockets so that ZMQ won't hang on exit