Leave out classes parameter for event simulation

[adrianSRoman]

This PR proposes adding a filter to ignore sound classes in simulation. Users may encounter this feature useful as some tasks in the development of SELD systems may require understanding behaviors and/or pitfalls that occur on some sound classes (not all).

The default value for the proposed parameter should be an empty list i.e []. The users may specify a custom list, which will ignore the classes contained by the list following the DCASE event class naming convention.