Placement elevation check, UI++

- ui
  * Area::DISABLED_BIT, HIDDEN_BIT, IGNORE_BIT ~> ENABLED_BIT, VISIBLE_BIT
  * CreditsMenu scrolls in both directions
  * BuildMenu
    + building placements checks terrain elevation
    + bounding box check rotation fixed
  * ui.showBuild setting removed
- client
  * window.desiredWidth -> window.windowWidth etc.