Refactoring the code of the combined analysis

I'm currently trying the refactoring of the code of the LST-1 + MAGIC combined analysis. Now I finished the scripts "magic_data_cal_to_dl1.py" and "lst1_magic_data_event_coincidence.py", and the refactoring of the other ones are ongoing. Once they are done I will re-commit them (So please still don't merge it).

Thanks to the refactoring, the modules can be imported now, and so I changed the directory name from "LST-1_MAGIC" to "lst1_magic". For example, the module "magic_cal_to_dl1" in the script "magic_data_cal_to_dl1" can be imported as follows:

from lst1_magic import magic_cal_to_dl1

Also, I put some functions to utils/my_functions.py script, and the functions can also be imported anywhere.

By the way, while refactoring the script for the event coincidence, I found a mistake in the calculation of the averaged time offset. Actually the results doesn't change so much, but I corrected that part of the script.

So any reviews/comments/suggestions are very welcome!!

Best regards, Yoshiki