getblocktemplate
getblocktemplate [params]
Returns data needed to construct a block to work on:
  "version" : block version
  "previousblockhash" : hash of current highest block
  "transactions" : contents of non-coinbase transactions that should be included in the next block
  "coinbaseaux" : data that should be included in coinbase
  "coinbasevalue" : maximum allowable input to coinbase transaction, including the generation award and transaction fees
  "target" : hash target
  "mintime" : minimum timestamp appropriate for next block
  "curtime" : current timestamp
  "mutable" : list of ways the block template may be changed
  "noncerange" : range of valid nonces
  "sigoplimit" : limit of sigops in blocks
  "sizelimit" : limit of block size
  "bits" : compressed target of next block
  "height" : height of the next block
See https://en.bitcoin.it/wiki/BIP_0022 for full specification.