Fix Units demo map following the addition of the special filter templates in D215 / rP19302.

Expose the FindAllPlaceableTemplates function to the simulation to remove the hardcoded directory checks as suggested by fatherbushido.
Add the new special template directory from D176 / rP19323.
Move the code from XML to JS.

Differential Revision: https://code.wildfiregames.com/D277
Reviewed By: Vladislav