add a gitignore file to ignore the class files generated for jython libraries at runtime
add a gitignore file to ignore the class files generated for jython libraries at runtime

EuropeanSpallationSource/openxal,luxiaohan/openxal-csns-luxh,openxal/openxal,luxiaohan/openxal-csns-luxh,openxal/openxal,EuropeanSpallationSource/openxal,EuropeanSpallationSource/openxal,EuropeanSpallationSource/openxal,openxal/openxal,luxiaohan/openxal-csns-luxh,EuropeanSpallationSource/openxal,luxiaohan/openxal-csns-luxh,openxal/openxal,openxal/openxal