Additional state machine for topics handling

[MarcoLm993]

Mentioned in comment: #63 (comment)

The discussion came up for supporting SCAN's property checking, that requires to know at least the target or the origin of a specific event for checking a property on it. This is an issue when modeling ROS-topic communication, that could have more than one publisher and more than one subscriber on the same topic.
To address the limitation, we want to have an additional state machine that:

• receives all messages from all publishers
• sends the same events to the related automata
  While this is definitely required for SCAN, for the Jani conversion it is not completely obvious it makes sense, since it would come with the following strings attached:
• Each topic consists of 3 additional automata (1 for the topic itself and 2 for communication to and from the topic automaton, compared to the current state where there is only one automaton per topic)
• Each topic required 3 sets of variables (one for storing the new message (internal, might be also an array) and 2 for communication, currently only one set is required (global)

Needs to be checked out...