Add implementation for signal handling. Use generic signal handler in DDG4 for controlled shutdown on CTRL-C. Add test DDG4_SIGINT_handler in examples/DDG4

fixes some tests that can run in this case successfully now

Too much hassle to ensure that the list was not duplicating the entries in the list

The original implementation also caused infinite loop by appending to the list that was iterated over causing ddsim to use up all the memory and not do anything

Added a test with an example ddsim steering file

Move generator status setting to common place

GenerationActionInit: declare properties to access number of processed runs and events

Avoid having another level of quotes or b'' showing up in the wrong places

Co-authored-by: Andre Sailer <andre.philippe.sailer@cern.ch>