Bug fixes (GamePiece select)

* Empire.as
** added import for events and dispatch*
** unselect_piece()
*** un-selects current piece and returns it
* Army/Agent.as
** refactored animateSelect()
*** added comments
*** removed dispatchEvent() (on selectThis() now)
*** added TODO
* GamePiece.as
** selectThis()
*** removed if/else
*** calls this_empire.unselect_piece() if selected_piece
*** checks current vs this
**** if not -> as normal
**** added dispatchEvent(AddListenerEvent) (moving pieces)
** add/remove_highlight()
*** to public
* ViewPort.as
** houses
*** DarkenEdges
*** InfoBox
*** ControlPanel
New City.square() issue

destroy() for GamePiece before creating/adding city
Destroyed city bug

bug: Destroyed cities on end turn get reverted from destroyed city
Debugging split_agents_out()

Selecting Agent from city and moving out not working
  - trying to do combinePieces() instead of split_...

Fixed by calling send_agents_to() within split_agents_out() if piece !=
null

Cleaned and rearranged code in GamePiece added more comments
Popup issue

Fixed build/recuit popups
  - not showing because of the addition of ViewPort
Popup Fixes/additions

Added a 'close button' to all popups where allowed
Fixed battle popup
  - issue with moving to ViewPort
  - added back to empiresAtWar.as as well