LevelSelectionButton enhancements

[pixelzoom]

In #59 (comment) and #59 (comment), @jonathanolson had suggestions for enhancing LevelSelectionButton. I was going to investigate as part of #66 ("change requests for UI components"), but just handling the changes for status bars turned into a major project. And due to Equality Explorer deadlines, I can't afford the time to work on LevelSelectionButton.

The 2 enhancements from #66 were:

• scale height of score display background in LevelSelectionButton
• add optional "{string} title" for a RichText title to LevelSelectionButton

Assigning to @ariel-phet to prioritize ("low" or maybe even "deferred" imo) and assign. I don't need any of these changes for Equality Explorer.

[pixelzoom]

See FRACTION_MATCHER/LevelSelectButtonsAndTitleNode.

[ariel-phet]

@jonathanolson since this is not needed for EqEx, priority is low, but if you feel it is fairly quick, feel free to tackle while it is fresh.