City build/recruit fixes and BattlePopup/Alert additions

Fixed xml for buildings
Added ability to destroy a city
  * turns till city is completely removed
Generic Change status functionality
Changed City sizes (population)
Info box navigation

Allow user to click arrows to rotate between Empire.pieceArray
Help Slides and fullscreen button

* Added other help slides
** moving around stage
** Use arrow buttons to next piece
** Settlers build cities
* Added ability to determine between piece info and help slide
* toggle_fullscreen_btn()