Allow expressions as portraits

[Jowan-Spooner]

• should close Allow the use of variables when choosing portrait #2199

You can now use variables as portraits. You can also use expressions, for example if your character can have multiple genders, you could put those portraits in separate groups like this:

- male
   - default
   - happy
   - sad
-female
   - default
   - happy
   - sad

Then you can now use {Player.gender}+"/happy" as your portrait (assuming the Player.gender variable is either "male" or "female").
Note that this will be parsed when the portrait is set. It won't update the portrait live, in case you change the variable later, unless the portrait is set again with this expression!

Other stuff

• also stops duplicated portrait items from reporting name changes
• also adds a print_debug_moment() method to the DialogicGameHandler that allows to easily print the timeline and event for errors.