Add Waila support

- Change default value of TileEntitySpeaker.label to empty string
-- Fixes IllegalArgumentException "Empty string not allowed" caused by
calling NBTTagCompound#setString with null as the value
- Remove TileEntitySpeaker#translate method
- Change TileEntitySpeaker#send[Formatted]Message to return boolean
instead of int
-- Returns true when the say command was executed (result > 0)
- Fix localisation by renaming enUS.lang to en_US.lang (the correct
locale code)
- Add mcmod.info
- Only save the configuration if it's changed