Merkle Proofs and Blocks

I have reimplemented Merkle trees. Next up are blocks. I have changed the block header in the following ways:

• Instead of including a difficulty, I include the target. This increases the block sizes, because the target is 32 bytes instead of 4 bytes. This value is more precise.
• I have increased the timestamp to 64 bits because the 32 bit timestamp runs out in 2106. 64 bits lasts far longer.
• I have increased the nonce to 256 bits. That is because the 4 byte nonce in Bitcoin is not big enough, and miners have to change transaction order to mine. We should be able to change the nonce only to mine.
• I have added the block index. This simply gives a convenient way to verify the block index for anyone tracking the block headers.