Robustness

Robustness and bugfix and CI enhancements, including

• recursive checkcode linting in test_matlab.m
• make absolute_path failsoft (return relative path) if absolute path is not determinable. Some HPC have this issue but still work with relative path
• make model_setup() directly runnable as top-level / entry script
• rename xgrid.m to avoid namespace clash with improperly setup Matlab custom toolbox from other HPC project