Add some features to the DynamicLight

MR Description

• This MR adds a shortcut for the DynamicLight in the Interpreter and 2 features to the DynamicLight:
• The possibility to apply a light to a follower, by sending a negative Integer as the chara_id parameter of the add method.
• The started? command which tells if the DynamicLight is considered as running.

Notes to acknowledge before testing

• The DynamicLight won't crash when trying to send a negative Integer "higher" than the number of followers

Tests to realize

• Try to use the dynamic_light or the dyn_light command in the console (S.MI.dynamic_light / S.MI.dyn_light) or in an event: the system should point to the NuriYuri::DynamicLight module
• Create a DynamicLight event which enable it when entering the next map. Make sure to have followers following you (Pokémon and/or human).
• Use negative Integers to add lights to the followers: the followers should have their own lights when entering the map.
• When on the map with the DynamicLight on, try to call the started? method of the DynamicLight: it should return true if the lights are on.