Classes and VisibleClasses cleanup

[fatherbushido]

Since some releases like r15195, the difference between Classes and VisibleClasses is mainly visual (gui). The aim of the ticket is:

• update the classes list and add the visualclass list in xml schema help (Identy component)
• move the classes which should be moved to visibleclasses which (or finish that transition see r15315)
• remove useless or duplicate or inconsistencies (and do the ad hoc checks/modifications to the simulation code, the gui code, the ai code).

Currently:

List of Classes Animal, Apadana, ArmyCamp, Ashoka, BarterMarket, BoltShooter, Bow, Camel, Catapult, Celt, Chariot, Citizen, CitizenSoldier, City, CivCentre, Colony, ConquestCritical, Defensive, Domestic, DropsiteFood, DropsiteMetal, DropsiteStone, DropsiteWood, Elephant, Female, Fireship, FishingBoat, ForestPlant, GarrisonFortress, GarrisonTower, Gates, Healer, Heavy, Hero, Human, Human, Iberian, Immortal, Italian, Juggernaut, Kennel, Light, Lighthouse, LongWall, Market, Melee, Mercenary, MercenaryCamp, Naval, Naval, NavalMarket, Organic, Organic, Palace, Palisade, Player, PtolemyIV, Ram, Ranged, SeaCreature, SeaCreature, Shipyard, SiegeTower, SiegeWall, SpecialBuilding, StoneWall, Structure, Support, Syssiton, Theater, Tower, Town, Unit, Warship, Wonder, WoodenTower, Worker

List of VisibleClasses Archer, Barracks, Blacksmith, Camel, Cavalry, Champion, Chariot, Citizen, City, Civic, CivilCentre, Corral, DefenseTower, Defensive, Dock, Dog, Economic, Elephant, Embassy, Farmstead, Field, Fortress, Healer, Hero, House, Infantry, Javelin, Market, Mechanical, Medium, Melee, Mercenary, Military, Outpost, Pike, Ranged, Resource, Ship, Siege, Slave, Sling, Soldier, Spear, Stables, Storehouse, Support, Sword, Temple, Town, Trader, Village, Warship, Worker