Support inverted TrapDoor (BUKKIT-3390)

Similar to Steps and Stairs, TrapDoors now have the ability to be inverted controlled by the fourth bit (0x08)
http://www.minecraftwiki.net/wiki/Data_values#Trapdoors

Feature added in Minecraft 1.4.2
http://www.minecraftwiki.net/wiki/Version_history#1.4.2

    Trapdoors
    Can now be placed on the top half of blocks [34]
    Placement works similar to that of slabs and stairs


Added logic pulled from Step.java and Stairs.java


Associated issue: https://bukkit.atlassian.net/browse/BUKKIT-3390