Change error handling behavior at user level

[nmaterise]

I noticed that all of our try-except clauses call quit() after printing the exception message. In some cases, this is not desirable, for example if the user is sweeping a large number of files and wants to see the totality of the fits, regardless of errors. It might be helpful to have a switch at the level of the Resonator class to change the behavior from calling quit() to something else.