Sliding Doors

Adds double and single glass sliding doors. Automatiacally opens when units are approaching. Provides light from outside during the day. Doesn't require stairs. Unlocks after researching Sliding Doors. The mod is compatible with the Lock Doors mod. The mod is compatible with older savegames. For the modders: The mod contains a base class for sliding doors, that could be used to create sliding doors (normal or double) from different materials. The mod has no new entities - the glass door uses the metal double frame as base, with two french metal windows as door wings. Please add this mod as dependency, if some of you want to create mods with sliding door support. The sliding door properties could be found in Building property category "Sliding Door".