Thieves in the second level of the merchant quest can not be moved around anymore

Modules required engine field is now strict: it will only use this engine, no others
The game now supports multiple versions of the engine and of modules.
There is a "Update All" option in the main menu that will download updates for all installed modules, and update the engine if they require it
Savefiles are now tagged with the module version that created them, they will not be available if that version is not installed and will load with that version, even if it's not the newest one


git-svn-id: http://svn.net-core.org/repos/t-engine4@1467 51575b47-30f0-44d4-a5cc-537603b46e54