message: add function to know if a block is genesis or normal
diff: @@ -202,6 +202,12 @@ pub enum Block {
  MainBlock(normal::Block),
  }
  impl Block {
  + pub fn is_genesis_block(&self) -> bool {
  + match self {
  + &Block::GenesisBlock(_) => true,
  + &Block::MainBlock(_) => false
  + }
  + }
  pub fn get_header(&self) -> BlockHeader {
  match self {
  &Block::GenesisBlock(ref blk) => BlockHeader::GenesisBlockHeader(blk.header.clone()),
  