Update de.txt

fixed ß in ss
added Air conditioner
added Armchair (...colour)
added chair
changed (rote) Vorhaenge in (Rote) Vorhaenge
fixed glass table piece large
fixed Wooden Shutter (...colour) 
added skylight_frosted
added Table
added Table Lamp
added table_legs_wrought_iron
changed Arbeitstisch in Arbeitstischplatte
added Wood table large/small_round/small_square