Add option for verbosity in `epiparameter_db()`

[jamesmbaazam]

By default, epiparameter_db() prints the output to screen. This is sometimes undesirable especially in a pipeline as it produces extra information that might not be needed. Please consider adding a verbose argument to the function to control if the result is returned invisibly or printed to the console.

[athowes]

I agree that a verbose argument would be nice here.