Caches the loaded mod versions, so that GetEngineInfo doesn't read the
zip and json files everytime and returns about 1000 times faster.
Adds two missing includes.
The lobby froze multiple times every few seconds on updateGameList().
The gamesetup page was slowed down with every stanza sent and the
load savegame selection page was slowed down per savegame selection,
proportional to the number of installed zipped mods.
Introduced by: d5807cd59f and eca956a513
Differential Revision: https://code.wildfiregames.com/D1518
Reviewed By: wraitii
Comments By: Imarok (in D1512, P121), leper (in the lobby)
This was SVN commit r21823.