Fixed some old support and infill issues.
Fixes support problem #4295
Fixes Parts of interface layer extends beyond supports and cannot be printed
Fixes support missing under horizontal overhang #6058
Fixes Slicer double-traces small sections of Rectilinear Supports, causes
Fixes plastic buildup and nozzle crashes #4951
Fixes Add "Angle Interface layers" #2969
check for other instances during startup
send message with command line arguments if found and terminate
listen for those messages and load objects from paths in messages from them