hide credit display in attract sequence

This change really only impacts public arcade machines, which likely spend the majority of their time cycling through the attract sequence of screens.  Hide the text and help prevent screen burn-in.

The attract sequence is currently not accessible in Home mode.  Maybe that should be reevaluated...
hide "Press Start" text on TitleJoin's OffCommand

The text should hide when a user presses Start.  Minor, but it was annoying me.
better input handling on SelectColor

Attempt to join an an unjoined player that presses Start.  Don't if it's not permitted due to coinmode or other settings.