Get the edit monster abilities dialog all working and updated (except for editing individual abilities)

Game changes:
- Remove support for playing a sound and displaying strings when a monster is first seen, since these behaviours can easily be obtained by using the special node called in the same context.
Dialog engine changes:
- Support for changing the font size of LEDs
- When setting the page, a stack now applies a default value if the map is missing the required data
- Add utility "addPage" method to stacks
- If reducing the page count means the current page is deleted, a stack now switches to the last page

src/doxy/mainpage.md

@@ -127,7 +127,7 @@ The `<led>` tag accepts the following attributes:
 Attributes** above.
 * `state` - Specifies the starting state of the LED. Can be one of
 `red`, `green`, or `off`; defaults to `off`.
-* `font`, `size`, `color`, `colour` - See **Common Attributes** above.
+* `font`, `size`, `color`, `colour` - See **Common Attributes** above. Note that, for an LED, omitting the size attribute gives a different result than any of the possible values.
 
 The `<group>` tag
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