Some refactoring. Created the Verbs class to deal with everything verb
related. There I have the verb tree, as well as keeping track of the
verb groups and which group each verb belongs to (only may belong to one
at once). This can allow handling events by specific verb but also by
verb group (in which case any verb within the group will trigger the
event). On the other hand, Expressions now keep their line number for
better debugging and error messages to the end user.
Major refactor. Fiction scripts are now being parsed. There is still
some dead code to trim, but now the fiction and parser configuration
(vocabulary) are being loaded from the file. I still need to process
expressions when verb messages are received.