/dev/emc Item inspired by OpenBlocks /dev/null

The /dev/emc will consume all the cobblestone you pick up (after filling existing stacks in your inventory) and store it into EMC.

The /dev/emc can than be right clicked to get (random) Emeralds, Diamonds, Gold Ingots, Iron Ingots, Coal or Potatoes, consuming the EMC from the /dev/emc.

Currently Missing:

* You cannot open the /dev/emc to make it consume something else than cobblestone
* You cannot configure which items you can get when right clicking it
* Tooltip
* Crafting Recipe (I thought about something like: cobblestone + low covalence dust)
* Icon 
* Maybe make it upgrade-able, to have more slots, so one /dev/emc can consume different items
* I was not able to use `addItemStackToInventory` to add the items directly to the players inventory, so i used the `dropItem`-Method. Adding the items to the inventory should be prefered. (It gave the players more items than it should, without consuming emc)

What do you think?