detect spectre return code and act accordingly

[jverbrug]

e.g. when spectre fails or is killed, do not run gnt processing

[jverbrug]

fixed monte carlo, more robust, no more need to save all data; changed normal simulation trigger; resolved #49 #50 #48

→ <<cset 0acd88f53c85>>

[jverbrug]

fixed monte carlo, more robust, no more need to save all data; changed normal simulation trigger; resolved #49 #50 #48

→ <<cset 50e8b53791cf>>