job shop: filter visible stations by _class, not id
allow configuring operationType on job shop machines
update PartJobShop example topology to have operationType set
add missing scipy import and remove unsued
test random number generator
RNG: validate parameters to prevent an infinite loop
Add a test topology with multiple replication and random distributions
make Machine use consisitent format for setupTime and loadTime
Do not modify seed on each run to have predictible results