Clear up signalIL/@function enumeration
During the last coordinators meeting (2023-05-02) it was decided to clear up the function enumeration of the signalIL in order to remove redundancies between infrastructure and interlocking. The general idea would to split IS and IL based on the following paradigm: everything that can be observed physically in reality should be described in IS while its meaning regarding interlocking functionality should be defined in IL.
One thing was decided in this meeting already, that is, that "main" should be removed from the enumeration in favor of its interlocking meaning, such as entry, exit or block, etc.
This work is to be conducted in a separate branch off the railML 3.3 development branch to be published with railML 3.3.