Add difficulty field to getblock / getblockbycount.
Add difficulty field to getblock / getblockbycount.

Add the difficulty as new field in the JSON representation of a block.
See https://github.com/namecoin/namecoin/issues/112.

fsb4000/huntercoin,chronokings/huntercoin,wiggi/huntercoin,fsb4000/huntercoin,fsb4000/huntercoin,chronokings/huntercoin,domob1812/huntercoin,domob1812/huntercoin,domob1812/huntercoin,chronokings/huntercoin,wiggi/huntercoin,fsb4000/huntercoin,wiggi/huntercoin,chronokings/huntercoin,wiggi/huntercoin,domob1812/huntercoin