Start stop add-on

[Danariki99]

Pull Request: Adds functionality to stop and restart a simulation without losing information, even when using the Physiboss add-on
The main changes include:

• I/O streaming operator added in the PhysiCell core (phenotype cells, customizations, etc.).
• start_and_stop_saving_files folder created to store the necessary files for saving.
• addon/start_and_stop folder with examples.
• Example capability to monitor and automatically stop a simulation in the use case.
• sample_projects_intracellular/boolean/spheroid_TNF_model implemented in the custom.cpp file.
• Start and stop examples added in sample_projects_intracellular/boolean/physiboss-cell-lines and sample_projects/biorobots examples.