Spark Panel displays incorrectly if either width or height is not specified

If you specify _both_ width and height (either numbers or percentages) for a Spark Panel, then all is OK.

But if not... I cannot even begin to describe the problems in the title bar:

Without height specified (second panel in the picture), the border is missing (or up against the bottom of the title bar).

[TestSparkPanel.mxml.txt](https://github.com/apache/royale-asjs/files/5623066/TestSparkPanel.mxml.txt)

Start with the attached TestSparkPanel.mxml.txt reproduction and inspect the Spark Panel implementation and its title-bar layout behavior. Reproduce the case with width or height omitted, then verify that the panel border and title bar render correctly in both partial-size cases.

Written by the indexing model from the issue text.