Removed hidden exit from the displayed exits.
Just working on the game.
Added the Hidden status.
Added a lift action.
Hidden room should display a particular text. Plus method for nice
presentation of objects, but it's wrongly used there.
Replaced a santence.
Door method. Still unperfect, but improving.
Articles are not parsed anymore.
Matching for objects is done after lowering case.
Test back without articles.
Rooms modified, now that they have a status of their own.
Added the guard room.
Made the no-room-found error message clearer.
Fixed graph connexion between hatch and corridor.