C# signal script extensions

For the C# signal script, the signal shape name will be added to the CsSignalScript class.
This could be used to determine the speed limit of the switchable speed sign (for existing signals which signal type doesn't indicate the speed limit).

Also, initialization of C# signal scripts will be reworked a bit because, currently, in the Initialize function, all of the functions are not available since WorldObject is not yet defined (impacts sig_feature for example).

Also, currently, when we set a signal with C# signal script to STOP using the dispatcher window, the behaviour of other signals can be weird because the signal no longer has a text aspect.
So, instead of forcing the state of the signal, jf a C# signal script is present, an event will be sent to the script and this script update the signal to a coherent state. And the hold state of the signal will be made available to the script.

Finally, the Signals.cs will be refactored in order to move each class to its own file.