empires: partial fix ui double focus
empires: partial fix ui double focus

It is still possible to have multiple buttons with focus, but the main
method to achieve this has been fixed. Also, buttons may now optionally
play a button click sound (we don't use this yet).

FolkertVanVerseveld/aoe,FolkertVanVerseveld/aoe,FolkertVanVerseveld/aoe