Added for_all_unique/3
added generate_unique/2.

Need a better name.
Fixed bug in Term.Sort() and Term.KeySort()

Broke for lists of length 1.  D’oh!
Augments stack trace for PrologErrors

Now includes C# stack trace for the underlying error.
Fixed documentation for generate_unique/2.
Added Is GameObject.IsCharacter() and .IsProp()
Major refactoring of event, action, and NL code

Event and action handlers now take event as first arg; this is more
readable and will allow easier indexing in the future.

Construals now supported
propose_once/1 removed