Add missing descriptions for new tests

#DESC run basic simulation of cosmics shower

[AllPix]

number_of_events = 1

detectors_file = "detector.conf"

#DESC check if the target simulation altitude can be configured

[AllPix]

number_of_events = 1

detectors_file = "detector.conf"

#DESC test if the correct subbox letngth for the simulated shower is calculated from the detector model and world volume

[AllPix]

number_of_events = 1

detectors_file = "detector_large.conf"

#DESC check if the emission of neutrons can be switched off effectively

[AllPix]

number_of_events = 1

detectors_file = "detector.conf"

#DESC check if the latitude can be changed effectively

[AllPix]

number_of_events = 1

detectors_file = "detector.conf"