Added customizable splash page.

If teaser count (of the @Home agent, which exports as index.html) is set to zero, BoxPress now replaces the teaser-style homepage with a Splash page that you construct with aliases (just like the navbar).

When the teaser count is > 0, the Home page shows a series of truncated POST teasers, as before.

Added widget in the Macros Dash to control appearance of the CARD background option for the Splash page.

Card border now controls both the pad (used when BKG-COLOR is set) background style and the CARD background style.