-Added a management window to creategame, which allows you to save and load

-Added a management window to creategame, which allows you to save and load
game, weapon and maplist settings.
-Added 'show score' and 'toggle console' to the controls menu.
-Fixed fopen in the menu (strips off data/ from the path).
-If the menu loses input focus, it hides now (instead of regaining it
use #define BRAVEMENU to force the latter behavior).
-Added Data_ExecString and the ITEM_DATA_SAVE_EXECSTRING event to make it
 possible to save the value of a cvar in a config conform way.
-The maplist now uses the cvars g_maplist and g_maplist_index.
-Added Item_DataLink_Nex_FileList.
-Added Nex_MessageBox.

git-svn-id: svn://svn.icculus.org/nexuiz/trunk@439 f962a42d-fe04-0410-a3ab-8c8b0445ebaa